Thick black smoke billows from a construction site where a fire rages in the Karakida district of Tama, western Tokyo, on July 26. (Video compiled from footage taken by Kenji Notsu and readers)

Police will launch an investigation into a fire that engulfed a construction site in Tama, western Tokyo, on July 26 that killed five people, injured at least 40 others and filled the sky with thick black smoke.

All five fatalities were male construction workers and 25 of the injured are in serious condition.

The fire brigade received an emergency 119 phone call at around 1:50 p.m. alerting them to the blaze that broke out at the building under construction with three floors above ground and three below in the Karakida district of Tama.

The fire was almost extinguished at around 7:30 p.m., according to the Tokyo Metropolitan Police Department and the Tokyo Fire Department.

Police will determine if the site had a fire safety problem and will investigate the case on suspicion of professional negligence resulting in death and injury.

The blaze broke out beneath the third-level basement floor in the building’s “seismic isolation layer” that absorbs sway energy to protect the structure against earthquake damage.

About 5,000 square meters of urethane insulation material caught fire when sparks from workers’ gas torches being used to cut steel scaffolding frames landed on it.

The sparks apparently dropped through a crack in the floor of the third basement level and set fire to the insulation in the ceiling of the seismic isolation layer, said investigative sources.

One worker was in charge of cutting the steel while another extinguished the sparks with water. The two initially tried to put out the fire with an extinguisher and water, but they could not combat the fast-growing blaze.

The workers started to evacuate after telling their team leader, who was in the space where the fire broke out, “It’s over for us,” according to the sources.

A qualified fire marshal had been selected for the construction team, and a firefighting plan had been formulated for the site in accordance with the Fire Defense Law, the Tokyo Fire Department said.

A fire drill had been conducted with the Tokyo Fire Department in attendance, and the department calls for measures to be taken to cordon off areas where sparks fly during construction work.

About 320 workers were at the construction site on the day. A 51-year-old worker was found dead on the rooftop, one man aged 52 and another aged 44 were found dead in the third basement level, while a 49-year-old man and another in his late 60s were found in the seismic isolation layer.

The office building, about 1 kilometer southwest of Karakida Station on Odakyu Electric Railway Co.'s Odakyu Tama Line near a commercial complex and a residential area, was scheduled to be completed this autumn, according to Hazama Ando Corp., the contractor of the site.

“LIKE A BATTLEFIELD"

Thick black smoke quickly filled the office building, where construction work was nearly complete, as the fire raged.

Many workers inside the building narrowly escaped while being enveloped in the smoke.

Voices were heard screaming “Fire!” and “The urethane is on fire!” from the third basement level.

A 38-year-old worker who was engaged in electrical work rushed to find the stairs to go up and evacuate.

He was instantaneously engulfed with smoke and the smell of burning, but managed to move away from the source.

On the way out, he saw a man collapsed face down on the floor.

“Hang in there or you will die!” he told the man, lifting him up.

He rushed up the stairs, which he could barely find.

When he went outside, many workers were on the ground suffering coughing fits.

“It was just like a battlefield,” the man recalled.

A 44-year-old man who had been installing air-conditioning equipment in the seismic isolation layer was also engulfed with black smoke immediately after the alarm was sounded.

It was pitch black inside the space due to a power outage.

With the light of his head lamp and yellow cones lined up along the gangway as his only remaining hope of escaping, the man made it to the stairs to evacuate.

While he was fleeing to safety, he saw yellow smoke on the third basement level.

“I could die if I inhale the smoke,” he said he thought.

He also heard frequent explosive sounds like that occur when a gas cylinder blows out.

“I just willed myself to get out no matter what,” the man said.

The suffocating black smoke also enveloped workers on the levels above ground.

“I couldn’t see anything even 10 centimeters ahead,” said a 36-year-old worker carrying out interior work.

“I have never been instructed on how to evacuate in the event of a fire,” said the man, who started working at the site about one month ago.

Another worker who said he participated in a fire drill held at the site two or three weeks ago said that there must have been people who didn’t participate due to a rapid turnover of workers at the site.

A 41-year-old worker who evacuated from the second floor said that fire extinguishers were installed on each floor of the building.

A parking lot of a convenience store near the scene was filled with workers who managed to escape the blaze.

A 77-year-old local former nurse looked after two male workers. One was semi-conscious and was having trouble breathing properly.

Another worker also complained of agonizing pain. Local residents brought ice and towels to comfort the two victims.