Two people dead, 10 others injured in explosion at US Steel plant in Pennsylvania

An explosion at a US Steel plant near Pittsburgh, Pennsylvania, left two people dead and at least 10 injured on Monday, heavily damaging the sprawling facility, officials said.

One worker was pulled from the wreckage hours after the explosion sent black smoke spiralling into the midday sky in the Mon Valley, a region of Pennsylvania synonymous with steel for more than 100 years. Authorities later said a second person had died.

Allegheny County Emergency Services said a fire at the plant started around 10:51 a.m. local time and that the explosion, followed by several smaller blasts, which some residents of a nearby community said was felt.

The explosion prompted county officials to warn 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 local media. “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.”

Cause of explosion under investigation

Local officials 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, US Steel’s chief manufacturing officer Scott Buckiso said at a news conference.

Buckiso said the company, now a subsidiary of Japan-based Nippon Steel Corp., is working with authorities. US Steel CEO David B. Burritt said the company would thoroughly investigate the cause.

“I end every meeting and every message with the words, ‘Let’s get back to work safely.’ That commitment has never been more important, and we will honor it,” he said in a statement.

The county's local hospital, Allegheny Health Network Hospital, said it received seven patients from the plant who were treated, with five already discharged, while the University of Pittsburgh Medical Centre said it is treating three patients at UPMC Mercy, the region’s only level one trauma and burn centre.

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 U.S. 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.

According to the company, the plant has approximately 1,400 workers, but in recent years, the Clairton plant has been plagued by concerns about pollution.

Long history of pollution concerns

In 2019, the steel plant consented to pay $8.5 million to resolve a complaint about air pollution. Five years later, the firm settled a federal lawsuit brought by the Allegheny County Health Department, PennEnvironment, and Clean Air Council, agreeing to spend $5 million on local clean air initiatives and programs and $19.5 million on equipment modifications.

The lawsuit stemmed from a Christmas Eve fire in 2018 that caused $40 million in damage. The fire damaged pollution control equipment, leading to repeated releases of sulfur dioxide, according to a lawsuit.

In the wake of the fire, Allegheny County warned residents to limit outdoor activities, with residents saying for weeks afterwards that the air felt acidic, smelled like rotten eggs, and was hard to breathe.

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.