At least one person has died, one person remains unaccounted for, and at least 10 people have been injured following multiple explosions at the U.S. Steel Clairton plant on Monday.
First responders were alerted to the incident just before 11 a.m. at the plant, which sits along a bend in the Monongahela River south of Pittsburgh.
At an afternoon press conference, officials said a search and rescue operation remains active to locate the lone unaccounted-for employee. Officials believe they know the location of the person, but are not “100% sure,” said Scott Buckiso, executive vice president and chief manufacturing officer at U.S. Steel.
Sources relayed to KDKA-TV that the explosions occurred inside the “reversing room” between batteries 13 and 15. The room acts as a mechanical regulator, making sure the coal bakes evenly in the oven. The plant has since been stabilized.
There were multiple secondary explosions reported, Allegheny County police later confirmed, with the county adding that the secondary explosions did not cause any “major injuries.”
Credit: CREATE Lab / Breathe Project 
The victim who died was later identified as 39-year-old Timothy Quinn.
UPMC officials confirmed to KDKA-TV that they received three patients at UPMC Mercy Hospital.
An Allegheny Health Network spokesperson also confirms that “multiple AHN hospitals are receiving inbound patients.”
At least five patients were transported to Jefferson Hospital, one patient was transported to Allegheny General Hospital and another patient was hospitalized at Forbes Hospital.
Those patients at Jefferson Hospital were discharged as of 4:20 p.m., an AHN spokesperson confirmed to KDKA-TV.
In all, officials said 14 local fire departments and 20 EMS services responded to the scene to assist.
U.S. Steel responds to explosions
U.S. Steel issued the following statement Monday afternoon following the explosion.
“Around 11 a.m. ET on Monday, August 11, an incident occurred at U. S. Steel’s Clairton Plant, specifically at coke oven batteries 13 and 14. Emergency teams were immediately dispatched to the scene.
‘Our top priority is the safety and wellbeing of our employees and the environment. We are working closely with relevant authorities to investigate the cause of the incident and will provide additional updates as they become available. 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.'”
David Burritt, president and chief executive officer of U.S. Steel, said in a statement, in part, that the company is “committed to providing every possible resource and support during this unimaginably difficult time.”
Clairton Mayor Richard Lattanzi spoke with KDKA-TV after the incident.
“The mill is such a big part of Clairton. For anyone that works, how old or young you are, you have to work every day, you need to go home healthy, and some people are not going to see the same husband or son or somebody that’s working the mill. It’s just a sad day for Clairton,” Mayor Lattanzi said.
Pennsylvania lawmakers react to explosions
Gov. Shapiro and Lt. Gov. Austin Davis issued statements on social media, saying the administration remains actively in touch with officials in Clairton. The Pennsylvania Emergency Management Agency and the Pennsylvania State Police have offered assistance.
Sen. John Fetterman (D) confirmed that at least one person remains unaccounted for.
“My team and I are tracking this explosion and waiting for more information. For those in the area, please listen to local officials and avoid the area,” Sen. Fetterman said. “Keeping those injured and all who are impacted in my thoughts right now.”
Credit: KDKA 
Sen. Dave McCormick (R) also released a statement following the explosions.
“Thinking about all those involved in and responding to the explosion at the steel plant in Clairton. I’m monitoring this closely as additional details become available, but in the meantime Dina and I will be praying for all those endangered and their families.”
“I’m closely monitoring the horrible tragedy at Clairton Coke Works,” Congressman Chris Deluzio (D) said. “My team and I are in touch with the United Steelworkers, United States Steel Corporation, and the Office of the Allegheny County Executive Sara Innamorato. I urge folks to follow guidance from local authorities and keep clear of the area. My heart goes out to these workers and their families, who will need all of us to rally around them.”
“Today’s tragic events have left our entire region shaken,” Sen. Kim Ward (R) said. “My heart and prayers are with the families enduring unimaginable worry and grief. I am deeply grateful for the swift and selfless actions of first responders and rescue crews who continue working under stressful conditions.
“For generations, U.S. Steel and the Clairton Coke Works plant have stood as symbols of Western Pennsylvania’s work ethic and determination. Our region’s story has been forged in the heat of steel mills by people who do not back down from challenges but instead stand shoulder-to-shoulder in hard times.
“In the face of heartbreak, we will not waver – because in Western Pennsylvania, we are forged in steel and we do not break.”
Stay-at-home-order lifted
The Allegheny County Health Department said in a Facebook post on Monday evening that the order to stay indoors has been lifted, and residents can resume normal activities
Previously, the department advised residents within 1 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.
KDKA-TV 
The health department’s air quality monitors have not detected levels of PM2.5 and sulfur dioxide above federal standards, the department said in a media release.
What is coke, the substance made at the Clairton plant?
U.S. Steel says the Clairton plant is the largest coke manufacturing facility in the country. Coke is a fuel used to melt iron ore, and it’s produced by baking coal in coke ovens.
The Clairton plant has ten batteries, which are a series of coke ovens, stacked in rows.
Clairton produces more than 4 million tons of coke each year.