At least one dead, 10 injured after explosions at U.S. Steel plant near Pittsburgh

Multiple explosions at the Clairton Coke Works near Pittsburgh killed at least one person and injured 10 others, with one employee still missing, authorities said Monday.

At least one person was killed and 10 others injured in a series of explosions at the U.S. Steel-owned Clairton Coke Works, about 20 miles south of Pittsburgh, on Monday morning. Emergency crews were still searching for a missing employee in the aftermath of the blasts, which occurred shortly before 11 a.m. ET (1500 GMT) at the facility, part of a large industrial complex along the Monongahela River.

Firefighters worked to contain flames and heavy smoke billowing from the plant. Allegheny County Police Assistant Superintendent Victor Joseph said two employees were initially reported missing, but one was later found and taken to hospital. The other is still unaccounted for, and rescue operations continue.

"It's still a rescue mission," Joseph told reporters, adding that determining the cause would be "a time-consuming technical investigation."

David Burritt, president and chief executive officer of U.S. Steel, said in a statement that the company was cooperating with authorities to identify what triggered the incident. Scott Buckiso, the company’s executive vice president and chief manufacturing officer, said they believe they know the general location of the missing worker but could not confirm.

Pennsylvania Governor Josh Shapiro confirmed multiple explosions and said his administration was coordinating with local officials. "The scene is still active, and folks nearby should follow the direction of local authorities," he wrote on X.

Clairton Mayor Rich Lattanzi called it "a horrible day" for the city, long associated with the steel industry. The Clairton Coke Works is the largest coke manufacturing facility in the United States, employing about 1,300 workers. It produces about 4.3 million tons of coke annually through 10 oven batteries, heating coal at high temperatures to make a fuel used in blast furnaces for steel production.

Air quality monitors detected no dangerous rise in sulfur dioxide following the explosions, but residents within 1 mile of the plant were advised to stay indoors, close windows, and set HVAC systems to recirculate, Allegheny County Executive Sara Innamorato said.

The plant’s owner, U.S. Steel, became a subsidiary of Japan’s Nippon Steel in June after a $14.9 billion takeover. The acquisition faced prolonged U.S. government scrutiny over national security concerns before receiving approval.

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