CLAIRTON, Pa. (AP) -- An oven at a U.S. Steel plant near Pittsburgh exploded Wednesday, injuring 15 workers, at least two critically, and causing a fire that burned for hours, emergency officials said.
The blast in the coke oven at United States Steel Corp.'s Clairton Coke Works happened around 9:30 a.m., Allegheny County spokesman Kevin Evanto said. Fourteen workers suffered burns and another suffered chest pains.
Everyone had been accounted for, and the cause of the explosion was being investigated, union and company officials said. The Occupational Safety and Health Administration had a team of investigators on site, spokeswoman Leni Fortson said.
An air quality inspector at the plant at the time of the blast said he saw a large cloud of smoke that dissipated quickly, said Jim Thompson, manager of the Allegheny County Air Quality Program. Thompson said that and other factors indicate the explosion may have been caused by the gas used to heat one of the coke ovens.
Neighbors said they heard alarms at the plant but didn't know at first whether it was a real emergency.
"They always play their siren," said Tiarra Williams, 17, who lives on a hill overlooking the plant. A maintenance worker died in a September 2009 explosion at the plant, which sits in a valley along the Monongahela River about 20 miles south of Pittsburgh.
About 1,500 people work at the plant, said Michael Wright, head of the health, safety and environment department for the United Steelworkers union.
Coke, a raw material used in steelmaking, is coal that is baked for a long time at a high temperature to remove impurities. The coal is baked in special ovens, several of which make up a coal battery; there are 12 batteries at the Clairton plant.
The explosion happened in the B battery, which consists of 75 ovens. The battery is located on the northern side of the sprawling plant and was shut down after the explosion. The other batteries remained open.
U.S. Steel calls its Clairton plant the biggest coke manufacturing facility in the U.S., producing about 4.7 million tons per year.
At Pittsburgh's West Penn Hospital, two workers in their 50s were in critical condition with chemical burns in their airways as well as burns to their heads, necks and faces, said Dr. Larry Jones, the hospital's director of emergency medicine.
"The burns themselves are serious burns, but with the inhalation injury on top of it, these are very, very serious, a very serious situation," Jones said.
A third worker, in his 40s, was in serious condition with burns on his head, neck, face and hands, and an ankle fracture, Jones said.
Six workers were taken to UPMC Mercy, which has a burn unit, said Gloria Kreps, a spokeswoman for UPMC hospitals. Another injured worker was taken to UPMC McKeesport, and three were taken to UPMC Presbyterian, she said.
She did not have information about their conditions.
William Magyar, 44, of McKeesport, was cleaning a rental property near the plant when he said he heard alarms around 10 a.m.
"I figured it was a fire I didn't smell," Magyar said.
Elaine Lawrence, 53, whose son works at the plant, was lying on the couch at her Clairton home when her daughter told her there had been an explosion. The daughter drove her to the plant, but they weren't allowed in; they headed to a hospital, and that's when her son called.
"He said he had just passed where the explosion happened to go to the other block and suddenly he heard an explosion," Lawrence said. Martin Lawrence, 19, was not injured and remained at work, she said.
"I was real concerned, because that's my only son," she said.