Aug. 18: U.S. Steel released a statement on Friday saying that the explosion may have happened amid flushing a gas valve in preparation for planned maintenance.
Built-up pressure inside the valve led to failure, according to the company’s preliminary findings. Additionally, it caused coke oven gas to fill the area, which brought about the explosion.
“We want to reinforce that this investigation is in its early stages, and we will provide more information when we can,” U.S. Steel said. “Our focus remains on our employees and their families during this difficult time.”
Aug. 13, 2025: The U.S. Chemical Safety and Hazard Investigation Board has opened an investigation into the explosion on Monday that occurred at U.S. Steel’s coke works plant in Clairton, Pennsylvania.
The explosion killed two workers and injured at least 10, according to the CSB press release. The explosion happened at around 11 a.m. EST, specifically at the Clairton facility’s coke oven batteries 13 and 14, U.S. Steel said in an email statement.
Multiple secondary explosions followed but did not cause any major injuries, according to an Aug. 11 Facebook post by the Allegheny County Government.
The Clairton facility processes raw coal into coke, which is used as a component in making steel, according to the CSB press release. The “massive” facility, located about 15 miles outside of Pittsburgh, spans 392 acres and employs nearly 1,300 workers.
“The CSB will work to determine the cause of this tragic incident and identify actions that can be taken to help ensure that a similar disaster like this does not happen again,” CSB Chairperson Steve Owens said in a statement.
The Allegheny County Police Department’s Homicide Unit has been requested and will lead the investigation in conjunction with the Allegheny County Fire Marshal and the U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives, local officials added.
“We are fully cooperating with all investigations into the incident, and we are committed to understanding exactly what happened so that nothing like it ever happens again,” U.S. Steel President and CEO David Burritt said in an emailed statement. “But right now, our focus is — and will remain — on our employees and the broader Clairton community.”
U.S. Steel is working closely with local, state and federal authorities to “understand what exactly happened,” Burritt said at a Tuesday press conference.
“We're not going to speculate,” he said. “We’re going to let the people do their work and support them and that important job. We will share as much as we can, as soon as we can, and we will take every step necessary to keep our people safe. Safety is, and always will be, our number one priority every shift, every day, every facility, always.”
U.S. Steel’s parent company, Japan-based Nippon Steel, said in an email statement that it’s also working with the subsidiary to support the “healing and recovery process.”
“Nippon Steel is deeply saddened by the incident at Clairton. We extend our heartfelt condolences to the family, friends, and coworkers of the deceased U.S. Steel employees, and pray for speedy recovery of those injured,” said the company in an unattributed statement.
One of the workers, Timothy Quinn, was a second-generation steelworker and worked at the Clairton plant for nearly two decades, Pennsylvania Gov. Josh Shapiro said at a press conference on Tuesday.
“He went by the name of T.Q.,” Shapiro said. “T.Q. was a special person, a devoted father of three. Someone who I understood served as a mentor to the other steelworkers who were here, someone that apparently you would go to on a rough day when you needed a joke and when you needed your stones busted.”
The family of the second worker who died wished to keep their identity private, Shapiro added.
“The USW has occupational health and safety experts and other representatives on the ground at the Clairton Works assessing the situation and aiding our members,” United Steelworkers District 10 Director Bernie Hall said in an Aug. 11 statement. “While we are still determining the scope of the tragedy, we are aware that multiple workers are receiving medical treatment for their injuries.”
“In the coming days, we will work with the appropriate authorities to ensure a thorough investigation and to see that our members get the support they need,” Hall added.
Editor’s note: The story has been updated to include U.S. Steel’s own preliminary findings that they believe led to the explosion.
