Thedeadly U.S. Steel plant explosionthat killed two people and hospitalized nearly a dozen others near Pittsburgh happened ahead of planned maintenance, the company said. In preliminary findings, U.S. Steel said the Aug. 11 Clairton Coke Works Plant blast occurred when personnel were flushing a gas valve while preparing for maintenance at the Pennsylvania facility that processes raw coal into coke, which is used to make steel. Pressure built inside the valve, which led to valve failure, thecompany said in an Aug. 15 news release. Coke oven gas then filled the area and ultimately exploded with an ignition source. The company didn't specify the ignition source, saying that the investigation was in its early stages. The blast triggeredsubsequent explosions at the plant, which is located about 15 miles outside Pittsburgh in Allegheny County. The federal Chemical Safety Board, which hasopened an investigation into the explosion, didn't immediately responded to a request for comment on Aug. 16. Bernie Hall, District 10 director of the United Steelworkers union, said in a statement that it was early in the investigation, "so we need to learn more before speculating further." The blast killedTimothy Quinn, 39, and Steven Menefee, 52, according to the Allegheny County Medical Examiner. Ten people were hospitalized, while other workers onsite had minor injuries. The392-acre Clairton plantis considered the largest coking facility in North America, theChemical Safety Board has said. It employs nearly 1,300 people. Contributing: Jeanine Santucci, USA TODAY Eduardo Cuevas is based in New York City. Reach him by email atemcuevas1@usatoday.comor on Signal at emcuevas.01. This article originally appeared on USA TODAY:U.S. Steel releases preliminary findings on deadly facility explosion
