Firefighters spray water on the site of an explosion at U.S. Steel's Clairton Coke Works plant in Clairton, Pennsylvania, U.S. August 11, 2025 in this screengrab obtained from an aerial video. ABC Affiliate WTAE via REUTERS.

By Rich McKay and Julia Harte

(Reuters) -An explosion at a U.S. Steel plant near Pittsburgh on Monday has killed one person and injured multiple others, with at least two people missing, police said, as fire crews could be seen battling flames while heavy smoke rose from the facility.

The explosion occurred at about 11 a.m. at the U.S. Clairton Coke Works plant, which is owned by U.S. Steel, a subsidiary of Nippon Steel.

Allegheny County Police spokesman Jim Madalinsky said at least two people were missing, as well as reporting the one fatality and multiple injuries.

The extent of the injuries was not known, but news accounts said that several people were taken to hospital burn units.

There was no word yet on a possible cause of the explosion.

Clairton Mayor Rich Lattanzi in a phone interview with Reuters from the site described the scene.

"I don't know if people are trapped," Lattanzi said. "There are ambulances and police and news media everywhere. It's a horrible day for Clairton. We're praying for everyone involved. We're just praying this isn't as bad as it looks."

Pennsylvania Governor Josh Shapiro posted on X that his administration was in touch with local officials in Clairton as they responded to the explosion.

"The scene is still active, and folks nearby should follow the direction of local authorities," he wrote, asking readers to join him in prayer for the Clairton community.

An official told CNN that some people were trapped under the rubble, and emergency crews were working to reach them.

The Clairton Coke Works, located on the Monongahela River south of Pittsburgh, is the largest coke manufacturing facility in the United States. Coke is produced by heating coal at high temperatures. It is used in blast furnaces as part of the process of making steel.

Clairton Plant operates 10 coke oven batteries and produces approximately 4.3 million tons of coke annually. The facility serves customers in the commercial coke market as well as U. S. Steel's steelmaking facilities.

In June, Nippon Steel, Japan's biggest steelmaker, closed its $14.9 billion acquisition of U.S. Steel after an 18-month struggle to obtain U.S. government approval for the deal, which faced scrutiny due to national security concerns.

(Reporting by Rich McKay in Atlanta and Julia Harte in New York; Editing by Leslie Adler)