'Like thunder': Worker dead, one missing after explosions at US Steel plant

Explosions at a US Steel plant that shook the ground near Pittsburgh have left one dead and sent at least 10 to hospitals, with emergency workers still searching the badly charred rubble hours later for a missing worker, officials said.

One worker was pulled from the wreckage hours after the explosions sent black smoke spiralling into the midday sky in the Mon Valley, a region of the state synonymous with steel for more than a century.

Allegheny County Emergency Services said a fire at the plant started around 10.51am.

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A search and rescue effort was still active on Monday afternoon local time and officials said they had not isolated the cause of the blasts.

The explosions sent a shock through the community and led to officials asking residents to stay away from the scene so emergency workers could respond.

“It felt like thunder,” Zachary Buday, a construction worker near the scene, told WTAE-TV.

“Shook the scaffold, shook my chest, and shook the building, and then when we saw the dark smoke coming up from the steel mill and put two and two together, and it’s like something bad happened.”

The search is ongoing for a missing worker

At a news conference, Scott Buckiso, US Steel’s chief manufacturing officer, did not give details about the damage or casualties, and said they were still trying to determine what happened.

US Steel employees “did a great job” of going in and rescuing workers, shutting down gases and making sure the site was stable.

Buckiso said the company, now a subsidiary of Japan-based Nippon Steel Corp., is working with authorities.

He also said search teams were still looking for one person who was missing.

They think they know the general location of that person, but weren’t sure, he said.

“Obviously, this is a tragedy that we want to understand,” Buckiso said.

Allegheny Health Network said it had treated seven patients from the explosion in its hospitals, and discharged five within a few hours.

University of Pittsburgh Medical Centre said it is treating three patients at UPMC Mercy, the region’s only level one trauma and burn centre.

Clairton residents like Amy Sowers, 49, felt an explosion nearby.

Sowers, who was sitting on her porch located less than a kilometre from the plant, felt her house shake.

“I could see smoke from my driveway,” she said.

“We heard ambulances and fire trucks from every direction."

Sowers decided to leave the area after she said she smelled a faint smell in the air.

Sowers, who grew up in Clairton, has seen several incidents at the plant over the years.

Despite health concerns, Sowers said many residents cannot afford to leave.

A maintenance worker was killed in an explosion at the plant in September 2009.

In July 2010, another explosion injured 14 employees and six contractors.

According to online OSHA records of workplace fatalities, the last death at the plant was in 2014, when a worker was burned and died after falling into a trench.

After the 2010 explosion, the Occupational Safety and Health Administration fined US Steel and a subcontractor $US175,000 ($268,000) for safety violations.

US Steel appealed its citations and $US143,500 in fines, which were later reduced under a settlement agreement.

“Lives were lost again,” Sowers said.

“How many more lives are going to have to be lost until something happens?”

The Clairton coking plant continued to operate after the explosion, although two batteries that were the site of the explosion were shut down, officials said.

Air quality concerns and health warnings

The plant, a massive industrial facility along the Monongahela River south of Pittsburgh, is considered the largest coking operation in North America and is one of four major US Steel plants in Pennsylvania.

The plant converts coal to coke, a key component in the steel-making process.

To make coke, coal is baked in special ovens for hours at high temperatures to remove impurities that could otherwise weaken steel.

The process creates what’s known as coke gas — made up of a lethal mix of methane, carbon dioxide and carbon monoxide.

Clairton Mayor Richard Lattanzi said his heart goes out to the victims of Monday's explosions.

“The mill is such a big part of Clairton,” he said.

“It’s just a sad day for Clairton.”

The Allegheny County Health Department said it is monitoring the explosions and advised residents within 1.6 kilometres of the plant to remain indoors and close all windows and doors.

It said its monitors have not detected levels of soot or sulphur dioxide above federal standards.

According to the company, the plant has approximately 1400 workers.

The plant has a long history of pollution concerns

In recent years, the Clairton plant has been dogged by concerns about pollution.

In 2019, it agreed to settle a 2017 lawsuit for $US8.5 million.

Under the settlement, the company agreed to spend $US6.5 million to reduce soot emissions and noxious odours from the Clairton coke-making facility.

The company also faced other lawsuits over pollution from the Clairton facility, including ones accusing the company of violating clean air laws after a 2018 fire damaged the facility’s sulphur pollution controls.

In February, a problem with a battery at the plant led to a “buildup of combustible material” that ignited, causing an audible “boom,” officials said.

Two workers received first aid treatment at a local hospital but were not seriously injured.

Environmental group calls for an investigation

David Masur, executive director of PennEnvironment, an environmental group that has sued US Steel over pollution, said there needed to be “a full, independent investigation into the causes of this latest catastrophe and a re-evaluation as to whether the Clairton plant is fit to keep operating”.

In June, US Steel and Nippon Steel announced they had finalised a “historic partnership,” a deal that gives the US government a say in some matters and comes a year and a half after the Japanese company first proposed its nearly $US15 billion buyout of the iconic American steelmaker.

The pursuit by Nippon Steel for the Pittsburgh-based company was buffeted by national security concerns and presidential politics in a premier battleground state, dragging out the transaction for more than a year after US Steel shareholders approved it.