A U.S. Steel plant south of Pittsburgh exploded Monday morning, killing at least one person and hospitalizing at least 10 more, authorities said.
One person remained missing into the afternoon following the explosion at Clairton Coke Works on the Monongahela River, Allegheny County officials said Monday afternoon. Pittsburgh station WTAE reported a second fatality was confirmed later that night.
The cause of the blast remains under investigation, U.S. Steel leaders said. In the immediate aftermath of the explosion, steel workers went in to rescue their comrades and stabilized the site to prevent further damage, Chief Manufacturing Officer Scott Buckiso said.
A fire at the plant about 10 miles south of downtown Pittsburgh started just before 11 a.m., Allegheny County Emergency Services said. Numerous ambulances responded to the scene.
“It shook my chest. It shook the building, then we saw the dark smoke rising from the steel mill,” construction worker Zachary Buday told local ABC affiliate WTAE. “Put two and two together. It’s like something bad happened.”
AP Photo/Gene Puskar
Emergency crews gather after an explosion at the Clairton Coke Works, a U.S. Steel coking plant, in Clairton, Penn. on Monday. (AP Photo/Gene Puskar)
The county health department warned people within a 1 mile radius of the plant to remain indoors and avoid drawing in outside air. However, county officials said soot and sulfur dioxide levels remained below federal standards for unhealthy air.
Though steelmaking is no longer the dominant industry of Pittsburgh, Clairton Coke Works is one of four U.S. Steel facilities in Pennsylvania, which still employ several thousand workers between them. The facility converts coal into coke as part of the steelmaking process.
“The mill is such a big part of Clairton,” Mayor Richard Lattanzi said. “It’s just a sad day for Clairton.”
Japanese company Nippon Steel purchased U.S. Steel for $15 billion in a purchase finalized in June following lengthy international and political negotiations.
Clairton Coke Works has run into problems in the past, with a small “boom” occurring inside the facility in February due to a “buildup of combustible material.” In that incident, two workers were briefly hospitalized but suffered no long-term injuries.
The plant was also the site of a deadly explosion in 2009, and another blast the next year injured 14 U.S. Steel employees and six contractors.
“How many more lives are going to have to be lost until something happens?” Clairton resident Amy Sowers asked.
With News Wire Services
Originally Published: August 11, 2025 at 1:29 PM EDT
