An explosion rocked a US Steel plant near Pittsburgh on Monday, injuring dozens of people and leaving some trapped under the rubble. The cause of the disaster is unknown.

There are no confirmed deaths from the incident, which first responders were alerted to just before 11 a.m. The explosion sent black smoke into the Pennsylvania sky.

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The plant, Clairton Coke Works, is located about 10 miles south of Pittsburgh in Clairton, Pennsylvania. The facility is considered the largest coking operation in North America.

Local news outlet WTAE spoke to someone near the scene at the time of the explosion.

“Felt like thunder. Shook the scaffold, shook my chest, then shook the building. Then we saw the smoke coming up from the steel mill,” Zachary Buday said.

Gov. Josh Shapiro (D-PA) and Rep. Summer Lee (D-PA) said they are aware of and monitoring the incident.

“My Administration is in touch with local officials in Clairton, PA as they respond to an explosion at US Steel Clairton Coke Works plant this morning,” Shapiro wrote on social media.

“@PEMAHQ and @PAStatePolice are in touch with first responders and have offered all assistance. The scene is still active, and folks nearby should follow the direction of local authorities. Please join Lori and me in praying for the Clairton community,” he added.

Sen. John Fetterman (D-PA) said he was on the scene and was “keeping those injured and all who are impacted in my thoughts right now.” He said dozens had been injured, and at least one person was unaccounted for.

Sources told KDKA-TV the explosion originated inside the “reversing room” of the 13/15 battery. The room acts as a mechanical regulator, ensuring that coal bakes evenly in the oven.

An explosion-like incident occurred in February at the plant, leaving two workers injured. A problem with a battery at the plant led to a “buildup of combustible material” that ignited, causing an audible “boom.”

TWO STATE TROOPERS SHOT IN PENNSYLVANIA

Pennsylvania, often referred to as “steel country,” is one of the top steel producers in the United States.

The Washington Examiner contacted the Allegheny County government and police, but received no response.