All language subtitles for Strange.Evidence.S06E06.Explosion.from.the.Underworld.1080p.MAX.WEB-DL.DDP2.0.H.264-BETHELL_track3_[eng]

[narrator] Worldwide,
36 billion cameras
are watching us.

On our streets, at work,
and in our homes.

They capture things
that seem impossible.

Science says this
shouldn't happen.

[person] Do you see that?

[narrator] Experts carry
out forensic analysis of
these unusual events.

Wow, what a blast!

[woman screaming]

This doesn't make sense.

There has to be
some sort of explanation.

What else is going on here?

[narrator] Coming up,
has the mother of
all stink bombs

caused this mystery explosion?

This is horrendous.
People were running
for their lives.

[narrator] Killer sludge
heads for an American town.

Anyone trapped under that
would be charred to a crisp.

[tires screeching]

[narrator] And a crashed van
spills unexpected cargo.

Seven, eight, nine,
ten... Oh my gosh,

how many people
are in this van?

There's still more coming out?

How could they
possibly have all fit inside?

[narrator] Bizarre
phenomenon...

Oh my god. [gasps]

-[narrator] Mysteries
caught on camera...
-[woman screaming]

What's the truth behind
this... Strange Evidence?

Sichuan Province,
Central China.

January 28th, 2020.

An early morning in
a city shopping district.

A security camera
films two young girls
playing on the street.

And then,
all of a sudden, boom!

The street lunges upward.

It happened so suddenly.
Giant concrete slabs
flying in the air.

[narrator] The two girls
and two other bystanders

disappear under
a pile of rubble.

There's a giant cloud
of dust, it's pandemonium.

People were
running for their lives.

That video is
absolutely horrific.

My first thought
watching that video is,

"Is that girl okay?"

[narrator] No deaths were
reported from the incident,

but the source of
the explosion is a mystery.

The scale of this blast
is off the charts.

It came out of nowhere.

[narrator] Former NYPD
image analyst, Connor McCourt,

notices the innocent looking
young girl is up to something.

The woman in
the purple jacket bends over,

and it appears she puts
something on to the ground.

And seconds later,
the entire ground explodes.

[narrator] There had been
over 80 terrorist attacks
in China since 2010,

but this isn't one of them.

Science journalist
Liberty Vittert believes

the girls may be
taking part in

a dangerous prank
that goes horribly wrong.

There's a widespread trend
in China of young children

dropping poppers and other
fireworks down manholes.

[narrator] When the black
powder in fireworks explodes,

it produces a sonic boom
of rapidly expanding gas.

The exploding
firework can reach

temperatures of
1800 degrees Fahrenheit.

If this happens inside
a confined space
like a sewer pipe,

the blast wave
can be amplified.

Has she just lit a firework
and dropped it down
the manhole?

[narrator] But the force of
this blast is far greater than
the energy

unleashed by a normal
sewer fireworks prank.

If you look at previous
fireworks explosions,

when it's thrown into a sewer,

the type of explosion you see
typically only lifts
the manhole cover,

or creates a small,
localized explosion.

That's not what
were seeing here.

[Connor] The force of
this explosion is incredible.

These planters here,
they're flown into the air

as the explosion erupts.

[narrator] Engineer
Brian Wolshon finds reports
of an explosive substance

infesting China's sewers,

a liquid that blights
the lives of its citizens.

So one of the hallmarks
of Chinese cooking,
is deep-frying things in oil.

[narrator] In 2018,
the Chinese used
over 34 million tons

of vegetable oil over
the course of the year,

to prepare more than
1.4 billion dinners per day.

The Chinese are
known to dump cooking oil

into sewer systems,
down a drain pipe.

[narrator] Cooking oil is
a prized possession in China,

and the demand far
outstrips the supply.

So criminals have turned
recycling into a disgusting
money-maker.

Gutter oil is a big
problem in China.

[narrator] This deadly,
second-hand cooking oil,

is harvested from
disease-drenched drains.

So there are criminal gangs

who are actually going
into the sewer system,

collecting this oil,

and then selling it back
to restaurants for use.

[narrator] It's estimated that
10 percent of all cooking oil
in China,

is oil that has been
scooped out of the sewers
beneath towns

and sold again for reuse.

They'll harvest it,
they'll filter a little bit,
strain it,

try to make it to where
it's presentable again.

And then, they'll sell it
back to the restaurants

that probably dumped
it there to begin with.

This is horrendous.
Sloppy goo from the sewer?

Surely, that can't be healthy.

[narrator] This highly
flammable sewer grease

isn't just revolting,
it's a health risk.

Gutter oil often contains
poisons that can
cause everything

from diarrhea
to abdominal pain.

It's even been linked
to cancer of the colon,

stomach, breast,
kidneys and intestines.

[narrator] The people of China
use over two million tons

of illegal gutter oil in
their cooking every year.

Street food vendors
are the number one
consumers of gutter oil,

but they're not the only ones.

Manufacturing facilities,
restaurants, supermarkets,

even school cafeterias have
been known to purchase
this product.

[narrator] Gutter oil is such
a health hazard in China,

that the authorities have even
introduced capital punishment

for criminals caught
collecting and selling
this slop from the sewers.

In 2014, Zhu Chuanfeng
was sentenced to death

for masterminding
a gutter oil empire

that netted him
over $4 million.

Criminals fearing
the firing squad
are now deterred

from scooping out
filthy fat from the sewers.

But this has simply created
a new, explosive headache
for the Chinese authorities.

The Chinese people are
walking on ticking time bombs.

[narrator] Coming up,
the ultimate dirty bomb
lurking in suburban sewers.

What might be
beneath your house

just waiting for
a firecracker to set it off.

[narrator] And is
this fur evidence

a polar predator is at
large in Washington state?

Given the opportunity,
they'd attack humans as well.

[narrator] In China, two young
girls are tossed into the air

when a fireworks prank
goes horribly wrong.

Historian Martin Morgan
believes their firecracker

has ignited
the filthy waste oil

that's been poured
down the city's drains.

A reality of the modern era
is the fatberg.

The idea that you get
a big buildup of fat

from cooking fats
that have been dumped
in the sewer system,

that all conglomerate
and congeal together.

[narrator] Already, they are
a massive problem in the west.

In 2017, a giant
fatberg is discovered

blocking up the Victorian
sewers of London.

This fetid mass of fat, oil,
feces, needles and diapers

is over 200 yards long,
and weighs the same
as 11 school buses.

It takes nine
weeks to dig it out.

Now, these greasy
monsters are growing

right beneath
Chinese citizens' feet.

These big, congealed fatbergs,

they are
potentially explosive.

[narrator] Fatbergs contain
cooking oil, methane
and hydrogen sulfide,

a potent cocktail
that could turn into

a fat-ferno, if
ignited by fireworks.

There's yet another
horror for you to imagine

each night when you lay down
to go to sleep.

What might be beneath
your house, is a fatberg

just waiting for
a firecracker to set it off.

[narrator] It's not known
exactly what caused

the fireworks prank to end
in such a catastrophe

but China has now told it's
cities to clean up their act,

and decreed that
sewers must be swept,

and their sludge
turned into clean energy,

perhaps in a belated
attempt to stop tragedies

like this one from
happening again.

Just think, those sewers
could be full of 10 years

of decomposing
nitrates and ammonia,

a dangerous cocktail,
waiting to explode.

[narrator] Now,
Gifford Pinchot
National Forest, Washington.

January 12th, 2013.

A lone hiker
deep in the forest,

finds and films a mysterious
white fuzz on a tree branch.

[Kevin] It's weird,
the entire stick is covered

with this strange,
glacial, white fur.

It looks like there's a stick
that's somehow grown
a long coat of white fur.

Trees don't grow fine
strands of hair, what is this?

[narrator] Gifford Pinchot
National Forest
is over a million acres of

mountains, thick forest,
and deep lava tube caves.

Deborah Hyde
wonders if the branch

has snagged the hair
of a polar predator
hiding out in the wilderness.

You often find tufts
of fur from animals

just caught on a piece
of tree as they've gone by.

This looks like
an extremely fine fur.

Sort of, beautifully white
like a polar bear fur.

[narrator] The polar bear's
North America's apex predator.

Over 12 feet long, it can
easily outrun a human,

and a single swipe
of its enormous paw
can decapitate a man.

And in recent years,
they've been migrating

closer to urban areas
in search of food.

In 2018, two Canadian men
are killed in separate
attacks by polar bears.

It's not hard to see how
some might connect this

white fur to these
terrifying creatures.

[Jon] Even though they live
in one of the coldest climates
in the entire world,

polar bears will
shed their fur,

their entire coat,
once a year.

[narrator] Image analysis
of the thin white strands

show that they are up to
two inches long
and densely packed together.

A polar bear's thick coat of
10,000 hairs per square inch

is made up of
similar looking strands.

Could there be a polar bear in
these woods shedding its fur?

[narrator] Polar bears can
prowl areas the size of Texas

and there's evidence that
they're heading down
from the Arctic.

In March 2021,
a bear in Russia
wanders 675 miles south,

terrifying villagers
in Dzhebariki-Khaya

before it is lured into
a cage, baited with seal fat.

But in the Americas,
it's highly unusual
for polar bears in the wild

to travel this far from their
usual Arctic hunting grounds.

James Bay, in northern
Ontario in Canada,

is the furthest south a polar
bear has ever been spotted,

and that's hundred of
miles away from this forest

in Washington state,
where we find this furry tree.

As we say in Texas,
that ain't no polar bear.

[narrator] Coming up,
is this a case of
tree-monic possession?

[Kevin] This tree
is a zombie tree.

It's both dead and alive.

[narrator] And seen
on a highway camera,

a small van crashes,
and over 40 people get out.

How could so many people
fit in the back of one van?

[narrator] In
a Washington forest,

a hiker discovers
a tree covered in
mysterious white hair.

And as the white tufts
come into contact
with the man's skin,

something strange happens.

It literally melts away at
the touch of his fingers.

[Deborah] This stuff
looks like animal fur,
but it doesn't behave like it.

If you touch it, it melts
away into the background.

[Ashanti] As I look a little
bit closer of this branch,

you can see that one end
of this kind of fuzzy,
white mass,

is actually attached to
the branch,
as if it were growing out.

This is not something
that trees normally do.

This lead me to believe
that this is caused by
some sort of fungus.

[narrator] What looks like
strands of hair,
is actually ice,

produced by a fungus
slowly attacking the tree.

It's a very rare
and unique case of fungi,
called Exidiopsis effusa.

[narrator] The fungus
is eating the tree
from the inside out.

This process
produces carbon dioxide,

which forces water
out of the wood.

Normally in cold temperatures,
water would freeze
like regular ice.

But the presence of
the Exidiopsis effusa fungus,

causes the water to
freeze into hair-like strands.

These icy strands
are a ghoulish byproduct

of the fungus's deadly
battle with the tree.

This tree is a zombie tree,

it's both dead, and alive.

[Jon] The fungus pushes
the moisture out of
the rotting wood,

into the atmosphere,
and it freezes.

And as it
continues to do this,

the strands of ice
grow longer and longer.

[narrator] As the fungus in
the wood eats its way through,

it releases
recrystallisation inhibitors,

similar to
antifreeze proteins,

that keep the hairs
in their unique shape.

The reason for this,
a mystery.

But scientists do know fungi
have developed many strategies
to lure and consume prey.

Fungi are both clever
and deadly,

and that is a very
dangerous combination.

Given the opportunity,
they'd attack humans as well.

[Kevin] They are linked to
all sorts of medical ailments,

and medical science
is struggling to keep up.

[narrator] Fungal infections
kill three times more people
than malaria each year.

In 2019, eight patients
die in British hospitals,

infected with a deadly
shape-shifting fungus
called Candida auris.

It was first discovered
in Japan in 2009.

It causes lethal
blood infections,

and has already
spread across the globe

killing half the people who
contract it within 90 days

and it's impervious to most
drugs and disinfectants.

So, fungus is incredibly
lethal to human beings.

[Jon] Fungi cells are
very similar to our own,

so it's very hard
to make medicines

that kill fungal cells without
also killing human cells.

[Ashanti] I've seen some weird
things growing out of trees,

but I've never seen
one growing a beard.

I'm never gonna look at
mushrooms the same way again.

[narrator] Now, a busy highway
on the outskirts
of Vienna, Austria.

August 15th, 2015.

A traffic camera records
a regular rush hour.

Okay, so we're seeing some
traffic cam footage here.

-[narrator] When suddenly...
-[tires screeching]

[Jayde] Oh, wow.

Well, that was a big crash,
with this white panel van
running into the railing.

Wow, the front end
is totally messed up.

[narrator] The van spins
to a stop right in front of
oncoming traffic.

Smoke billows out
of its smashed hood.

Okay, so we can see the driver
gets out of the van.

Well, that's good.
He looks like he's okay. Phew.

[narrator] Then, the side door
slides open.

Look at all those
people filing out of the van.

[narrator] Like
a dam giving way,

a wave of people spills
out onto the blacktop.

[Jayde] Five, six,
seven, eight, nine, ten.

Oh my gosh, how many people
in this van?

There's still more coming out?

I'm counting 12, 13, 14...
It just keeps going.

[Jayde] When you look at
the mass of those people,

compared to
the volume of the van,

there must be some
sort of extra space,

or a trapdoor that
we can't see in the footage.

[narrator] Incredibly,
nearly a minute after

the first person left
the stranded vehicle,
they are still coming.

Imagine being one of those
cars stopped beside the van,

you would be
absolutely shocked.

[narrator] Over 40 people
emerge from the damaged van

that's designed
to seat just three.

How could so many people
fit in the back of one van,
and where are they going?

[narrator] Coming up,
were these captives
in transit to a life of hell?

The slave trade unfortunately,
is still very much alive
and kicking.

[narrator] And the cable guy
gets the shock of his life.

[Carin] It's a living rope

and it's ravenously hungry.

[tires screeching]

[narrator] In Vienna, Austria,
a small van crashes
on the highway...

and over 40 people
spill out on to the road.

[Tracy] So initially when
I saw this clip,

what came to my mind were
clown cars from the circus,

where it's just clown
after clown after clown,

coming out of these
small cars.

This scene, with so many
people packed into
a small van,

looks like an illusion.

[Tracy] But you can see file
information on the camera,

and it doesn't look like
it's been tampered with.

How could they possibly
have all fit inside?

[narrator] Lots of
human beings can
fit into one vehicle.

In 2014, a group of 27 women

managed to fit into
a Mini, in Brighton, England,

-breaking the world record.
-[audience applauding]

A Mini has an internal
capacity of 19 square feet.

The van in the footage
may look significantly larger,

but still has less than
63 square feet of space.

Humans need about
300 square feet
to feel comfortable,

but they can survive
in far less space.

[narrator] But the women
in the Mini were crammed in

for just a few
claustrophobic minutes

and the vehicle would never
have been allowed to move,

let alone drive on
the highway.

Siobhan Deshauer
suspects the highway footage

shows something
sinister is going on.

[Siobhan] You would
never choose to be
crammed in like sardines

into the back of a van.

You can see the driver's
acting in a suspicious way.

At first, he seems
to be pacing back
and forth along the van.

Then he grabs something
from inside the van
and starts running.

He doesn't seem to be
concerned about
his passengers at all.

Could this be some kind of
trafficking operation
that's gone wrong?

The slave trade
unfortunately, is still
very much alive and kicking.

[narrator] The price of human
life has never been cheaper.

In ancient Rome,
the average price of a slave

cost about $10,000
in modern money.

The average cost of
a 21st century slave,

is just $90, the price
of a pair of jeans.

The number of modern
day slaves in Europe

is one of the highest
in the world.

And highways are the backbone
of this transcontinental trade
in human misery.

There's a human trafficking
route that runs from
eastern Europe to the Balkans,

and directly into Austria.

Could these people be
on their way to a life
of forced labor?

[narrator] If their
final destination
is Great Britain,

then the answer could be yes.

Over 10,000 people
live as slaves in the UK,

with the number
rising every year.

The people behind this
are disgusting parasites.

They're feeding off
of desperate people
hoping for a better life.

[narrator] Great Britain
abolished slavery in 1807,

but two centuries later,
shocking cases
continue to be found.

A traveler family in Britain
kept 18 people as slaves
for 25 years.

A lot of these people
are actually homeless

and they were promised
food, accommodations,

in exchange for
a few months of work.

[narrator] The traveler
family scours the country

and prey on vulnerable
people for their work gangs.

They keep their prisoners
in line with savage beatings
and malnutrition.

One man is even forced
to dig his own grave.

They keep them
in squalid conditions,

forcing them to work all day,
every day, for no money.

If they complained,
they were punished.

One man had a concrete
slab thrown in his face.

[narrator] It isn't
much better in America,

where up to 400,000 people
are trafficked into slavery
every year

and around 80 percent of them
are women and children.

Sometimes, only the victim's
family come to their rescue.

[Jayde] We've all
seen the movie Taken.

It was a real life case
of a 16 year old girl in Texas
that was kidnapped

and would have been
forced into a lifetime
of slave labor.

Fortunately, her father pulled
a real life Liam Neeson,

and was able to track
her down and rescue her.

But the reality for
a lot of people is that
they're not so lucky.

[narrator] But Chad Orzel
doesn't think

slave trafficking is
what we're seeing here.

[Chad] Looking more
closely at the footage,

we see that the people seem
to be all different ages.

It looks like there are
whole families in there.

Human traffickers
prey on individuals,
they would separate families.

So this must be
something else.

You know, with world conflict
the way it is
around the world,

you've got a lot of refugees
crossing borders.

And they'll do anything
to get across.

And something like this
is the result.

Maybe that's what
we're seeing here.

[narrator] At the end of 2019,

26 million people worldwide
are considered refugees.

They come
from warring nations.

Syrians who stay in Syria
risk being blown apart

by relentless
bombing campaigns.

People fled Sudan,
because rebels soldiers
at any moment

could choose to destroy
their villages.

Travelling in a cramped van
doesn't seem as big a risk

when you know what
you're trying to escape.

[tires screeching]

[narrator] That's until
something goes wrong.

[Jayde] So, this footage
was taken in August of 2015,

and in the same month,
in Austria,

police find another van
with the decomposing bodies

of over 70 people
that were crammed
inside there.

Day after day, people die
trying to seek refuge
in Europe by land or sea,

but this is one of
the worst cases.

[narrator] The men, women
and children in the footage

could have been cooped
up inside the van for days.

Just imagine if it had been
a worse accident,

all those people could have
been badly injured,
if not killed.

[narrator]
Following the crash,
the Austrian authorities

take the refugees in
for processing

but they do not reveal their
identities to the public.

To this day, the whereabouts
of the driver who fled
the scene remains unknown.

You know, it looks like
these people got away
with minor injuries,

but they were lucky
to get out alive.

[tires screeching]

[narrator] Now,
Costa Rica, Central America.

July, 2018.

An electrician is making
repairs to a dilapidated
village house

when he sees
a mysterious cable.

What appears to be
a black rope
or maybe even a wire.

[narrator] When he approaches,
he makes a shocking discovery.

[Shaena] It's moving.

This thing is alive.

I've never seen anything
like that before in my life.

[narrator] This is a cable,
where there's no cable.

This loop is made up of ants.

I think there's thousands
of ''em.

Woah!

This is fantastic!

Are ropes supposed
to crawl like that?

On first glance,
it looks like the ants

must be crawling over
something, like a rope.

But when you check
it out more closely,

what you can see is that
the ants are climbing over
their own bodies.

The rope is made of ants.

[Greg] It looks like they're
carrying larvae or eggs.

These ants are hunting.

I can see something
that looks like a wasp
or a bee nest attached to it.

[narrator] These ants
seem to be defying gravity.

[Greg] How did they get
from one point to the next?

How did these ants
build a rope

from the edge of the house
to the wasp's nest,

without anything in between?

How on earth is that created?

[narrator] Coming up,
is this evidence

of an ant species
suddenly getting smarter?

These living bridges
usually only get to be
about five inches long.

But this one is
absolutely immense.

It wouldn't surprise me
if there were thousands
of ants in this bridge.

[narrator] And a mysterious
black mass

sweeps towards
an American town.

Anyone trapped under that
would be charred to a crisp.

[narrator]
In the Costa Rican jungle,

a man films a gravity-defying
living bridge of ants
on a feeding frenzy.

Entomologist Kevin Kasky
studies the footage

and identifies
the ant species.

I think what we're looking
at is a colony of army ants.

And what's unique
about army ants

is they literally
march in a straight line.

Army ants don't build nests
in the ground like other ants,

instead, they're constantly
on the move.

[narrator] Army ants
are half an inch long
and practically blind.

They don't sound
like a military marvel,
but size can be deceiving.

Individually, an ant is
not much.

All they do is eat, sleep,
follow the queens orders.

But you put them together,
they form a cohesive megaunit.

[narrator] When ants
get together, they make
a gargantuan superorganism.

Some army ant colonies contain
as much as 20 million ants,

all controlled by one
single, autocratic queen.

[narrator] And this
single-minded military machine
has no permanent home.

It moves on a relentless
march through the jungle,

foraging like
a miniature Mongol horde.

Anything that
stands in their way

will be overwhelmed
and potentially destroyed.

The hunting parties
of army ants

can kill over 500,000
creatures a day.

[narrator] The army ant's
main weapon is their
large mandibles

that work like scissors
to slice open their prey.

The bite is very painful,

and because their jaws
are so strong and lock on,

it's very hard to remove them.

[narrator] Even if
the ant body is broken off,

the head will keep biting
down in a death grip.

Army ants are champion
athletes despite their size.

They race across the ground
at over four inches
per second.

A human travelling
at the same pace

would be going
at 37 miles per hour.

Most prey can't outrun them.

When they attack,
they swarm over the body,

you may not even
know they're there,

until a signal tells them
to all bite, nearly at once.

And there is no known
way to stop them

once they've started
their attack.

At the same time that they're
cutting and killing the prey,

they're also secreting an acid

which is sort of
digesting the creature
outside of the body,

making less work for them,
and leaving more time

for them to move
on to their next kill.

It would take a while for them
to gnaw through your
whole body.

But once they get started,
there is no stopping them.

As individuals,
ants are tiny and weak,

but when they band together
like this, they can be deadly.

[narrator] Any creature unable
to evade this army
will perish.

Hungry army ants
have been known to devour

cats and dogs
locked in houses.

[narrator] Most horrific
of all, they can target
small human children.

When a baby was
abandoned in a Russian forest,

she was found covered in ants
being eaten alive.

But luckily, she survived.

This is just horrific.
My skin crawls thinking
about it.

[narrator] Even
if the colony's prey is
raised up off the ground,

these ants can find
a way to reach it.

When army ants go hunting,

they can use
themselves as bridges

as a way to get over holes
or other obstacles
that could be in their way.

They don't plan it,
it's more of an instinct.

When one ant senses a hole
in the ground, it slows down,

but the ant behind it
keeps moving and walks up
onto its back.

[narrator] When enough
ants have done this,
the living rope gets stronger.

Like scaffolding, it allows
them to climb upwards,

getting closer to
the prey above them.

[Shaena] When an ant
feels another one on its back,
it freezes.

The ant on its back
sees the gap
and also slows down.

And that process
keeps repeating
until there's a bridge.

[narrator] Pulling off
such a feat
requires incredible strength.

An ant can carry around
50 times it's body weight,

the equivalent of
an average man

carrying two
rhinos on his head.

But an ant bridge
like this is one,
is an engineering miracle,

even for these
unstoppable creatures.

These living bridges usually
only get to be about
five inches long.

But this one is
absolutely immense.

It wouldn't surprise me
if there were thousands
of ants in this bridge.

[narrator] Scale analysis of
the Costa Rican ant cable,

shows that it's six feet
in length,

approximately 145 ants long.

That's the equivalent
of replacing

the Rio Grande Gorge
Bridge with a line of people.

The bridge probably
started out much straighter,

but as more ants joined it,
it got longer and heavier
and dipped further down.

[narrator] But the incredible
length of this living chain

suggests that the ants
maybe part of a colony
of unimaginable size.

There's thousands
of ants in this bridge.

That means that
there's probably

millions of other ants in
the colony out there

to make this bridge
worth their time.

I think this could be
an ant super colony.

Usually, ant colonies
only have one queen.

But sometimes,
several colonies
will work together

to increase their strength.

[narrator] The ant's main
purpose is to kill and eat

every inhabitant of the nest
that they are entering.

[Kevin] This is terrifying.

If they could build a bridge
that is that long,

think of what they can do
if they build a bridge
into my house

or worse yet, your house.

[narrator] There are already
over 10,000 trillion ants
on our planet.

Their next bridge
could be to your house.

As they start invading
into urban settings,

their numbers increase,
and who's next on the menu?
You and I.

[narrator] Now,
Pima County, Arizona.

July 15th, 2020.

A wildlife cameraman
hears a strange noise
in a quiet desert landscape.

[liquid gushing]

[narrator] Then, it appears.

[gushing continues]

In the distance, you can see
something rolling towards us.

[Jeff] It's kind of
alien-looking

and it's just
moving really quick.

And it's just,
kind of relentlessly
just oozing and pouring.

[Ashanti] This is
the Arizona desert.

Seeing this black fluid
rolling over the
parched desert, is so surreal.

[narrator] A mysterious sludge
coating everything in sight.

It looks like an avalanche
of black goo.

What is this sinister
black tsunami and
where did it come from?

[narrator] Coming up,
a wave of black death
sweeps into town.

You think you're finally safe,

but the worst
could be yet to come.

[narrator] In Arizona,
a tidal wave of black sludge

is filmed rolling
towards the city of Tucson.

Journalist Jeff Wise finds
reports of weird black goo
appearing all over the world.

There's a similar sort of
black goo

that's been reported
in Caracas, Venezuela.

They call it Le Mancha Negra,
the black stain.

[narrator] The black stain
first appears in 1986
on a road near the airport.

It's small at first.
An inch thick,
greasy black blob.

But it slowly
spreads to coating

an eight mile
stretch of highway.

The consistency of this goo
changes with the weather.

It's as if hot weather
makes it expand.

[narrator] The black
ooze has been blamed

for numerous traffic
accidents and even deaths.

Although it's very sort of,
oozy, it's also slippery

and that can cause cars to
kind of, spin out of control.

It's so dangerous that

taxi drivers refuse
to drive here when
the phenomenon appears.

They don't want to
risk their lives.

[narrator] As the black
ooze spreads,

the Venezuelan government
becomes more desperate
to get rid of it.

They try everything,
including pressurized hoses,
to try to wash it off,

but nothing works.

They've tried detergents
and other chemicals,

but that doesn't work either.

And they've even
tried to scrape it off

with a variety of implements,

but the black goo
continues to return.

To this very day,
they still don't know

what this weird
black substance is.

[narrator] But as the raging
dark torrent gets closer,

Nick Householder
spots a terrifying detail,

that marks it as different
to the black ooze that
appeared in Venezuela.

It seems like a mixture
of mud and sticks,

but it looks like
it's steaming hot.

[Jeff] So it's flowing
like water and yet
it's also smoking.

Like, it's apparently on fire.

It's like this moving,
smoking, churning mass.

Anyone trapped under that
would be charred to a crisp.

[narrator] Science historian
Ashanti Davis finds maps
show a forest uphill

from the place
where the footage was shot.

[Ashanti] It's just a lot
of burnt charred material.

That suggests that it might be
the product of a forest fire.

This footage was taken in July
which could be
prime fire season,

especially in
the Arizona desert.

[narrator] Local news reports
show that Arizona dealt with

over 2000 wildfires in
the summer of 2020.

Thousands of raging infernos
sweep across swathes
of tinder dry forests,

across the
American west coast.

They're propelled by winds
of over 60 miles per hour,

making the fires
impossible to outrun.

The remains of
one man were found

in the driver's
seat of his car,

with those of his grandmother
sitting next to him.

[narrator] In 2020, more
than 30 people are killed

and tens of thousands
are forced to evacuate
their homes.

Many of these fires were
caused by lightning strikes,

but some were set on purpose.

One man claims to have
started a fire in California,

to hide the bodies of
five of his murder victims.

[narrator] On June 5th, 2020,

a devastating fire breaks out
in Santa Catalina mountains
in Pima County.

It spreads across
over 100,000 acres

and is still burning on
the day this footage
is filmed.

But how could a fire
create a smoking river of goo?

If you look at
the background of the video,

you notice that
the sky is very cloudy.

It's monsoon season
in Arizona so,

lightening, thunder,
and just rain, rain, rain.

[narrator] The July storm
that swept in that day,
didn't snuff out the flames,

it merely stirred
up more trouble.

Extreme forest fires can
change the physical nature
of the soil below them,

almost creating
a waterproof layer

that liquid just slides
right off of.

This means that even
a light rain can turn into

an aggressive flood
with very little warning.

Large amounts
of burnt material

like ash, silt, rocks
and even burnt trees

become loose
and start rolling downhill.

[narrator] In 2018,
a forest fire
followed by storms

sends waist high mud
flowing through

California's Santa Barbara
County, at 35 miles per hour.

This water doesn't even behave
like normal water anymore,

it's more like wet cement.

This is a hardcore mudflow.

It picked up trees,
it picked up rocks.

Even picked up cars.

[narrator] 23 people
are killed.

The citizens of
Tucson were fortunate

that the killer sludge
didn't hit the town.

Next time,
they may not be so lucky.

As the rate of
wildfires increases,

the risk of these additional
disasters also increases.