(NewsNation) — Officials said multiple explosions at a U.S. Steel plant in Clairton, Pennsylvania, left two people dead and 10 others injured and another person missing.
Allegheny County Emergency Services said a fire at the plant started around 10:50 a.m. Monday between the 13th and 14th coke batteries at the U.S. Steel Clairton Coke Works, and it confirmed the death and injuries, many of which are not life-threatening.
The agency later made a statement calling the explosion “a Level 3 mass casualty incident” to allow for more EMS resources from across the region to respond. In a press briefing on Monday, county officials said search-and-rescue efforts were underway for one employee that is still unaccounted for.
Pennsylvania Gov. Josh Shapiro said all injured employees have been sent to a local hospital to receive care.
“Lori and I are eternally thankful for the bravery of our first responders — and we continue to pray for the entire Clairton community,” Shapiro said in a post on social platform X.
“It was a terrible incident and my prayers go out to all the families affected by this,” Clairton Mayor Richard Lattanzi said in a Facebook post. “There are people hurt and that is the utmost importance.”
The Allegheny Health Department is advising residents within one mile of the plant to remain indoors, close all windows and doors, set HVAC systems to recirculate and avoid activities that draw in outside air, such as using exhaust fans, “out of an abundance of caution.”
“Nearly 1,300 dedicated men and women work at the Clairton Plant each day, performing their jobs with the utmost safety. During times like this, U. S. Steel employees come together to extend their love, prayers, and support to everyone affected,” U.S. Steel President and CEO David B. Burritt said in a statement to NewsNation.
The Bureau of Alcohol, Tobacco, Firearms and Explosives announced that its Pittsburgh field office is assisting in efforts related to the explosion.
According to a local news outlet, the Clairton plant has been under fire in recent years for pollution concerns. In 2019, it agreed to settle a 2017 lawsuit for $8.5 million, in which the company agreed to spend $6.5 million to reduce soot emissions and noxious odors from the facility.
It has also faced other pollution lawsuits, including ones accusing the company of violating clean air laws after a December 2018 fire damaged the Clairton facility’s sulfur pollution controls.
U.S. Steel said it would be working closely with authorities in the investigation into what caused the explosion.
Pennsylvania Lt. Gov. Austin Davis said the state will provide resources during rescue and investigation phases.
A portion of the Clairton Coke Works, a U.S. Steel plant, is seen Monday, Aug. 11, 2025 in Clairton, Pa. (AP Photo/Gene J. Puskar) 
An emergency crew is seen after an explosion at the Clairton Coke Works, a U.S. Steel coking plant, Monday, Aug 11, 2025, in Clairton, Penn. (AP Photo/Gene Puskar) 
The Clairton Coke Works, a U.S. Steel coking plant, is seen Monday, Aug 11, 2025, in Clairton, Penn. (AP Photo/Gene Puskar) 
Emergency crews gather after an explosion at the Clairton Coke Works, a U.S. Steel coking plant, Monday, Aug 11, 2025, in Clairton, Penn. (AP Photo/Gene Puskar) 
This image provided by Amy Sowers shows smoke from the U.S. Steel Clairton Coke Works, Monday, Aug. 11, 2025 in Clairton, Pa. (Amy Sowers via AP) 
Emergency crew gather after an explosion at the Clairton Coke Works, a U.S. Steel coking plant, Monday, Aug 11, 2025, in Clairton, Penn. (AP Photo/Gene Puskar)