Clairton, Pennsylvania - A search and rescue operation was underway Monday after blasts at a Steel plant in Pennsylvania left at least one person dead and dozens wounded, officials said.

"Multiple explosions occurred today at U.S. Steel Clairton Coke Works," the state's governor Josh Shapiro said in a post on X, naming a plant some 15 miles outside the city of Pittsburgh.

"Injured employees have now been transported to local hospitals to receive care, and search-and-rescue efforts remain active at the plant," he added.

Allegheny County Police said in a Facebook post that emergency services were on the scene and "at this point, officials can confirm there has been one fatality in connection with this incident."

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Senator John Fetterman of Pennsylvania posted on X that "dozens" had been wounded.

Some media outlets reported that people were still trapped under the rubble of the explosion.

Clairton Mayor Richard Lattanzi told CBS there had been several injuries, some "maybe critically."

"I'm just so sad about this whole day," he said.

Videos on social media, not verified by AFP, appeared to show firefighters battling the blaze in front of a gutted industrial building, under a thick plume of white smoke.

Located on the Monongahela River, the Clairton Coke Works is the largest coking factory in the US.

US Steel did not immediately respond to a request for comment.