Preparations for a routine maintenance task may have led to an explosion at a U.S. Steel coal-processing plant near Pittsburgh that left two dead and sent 10 to hospitals, the company said Friday. U.S.

United States Steel said on Friday a fatal blast that killed two and injured 10 others at its Clairton Coke Works plant near Pittsburgh happened when flushing a gas valve, ahead of scheduled maintenance.

U.S. Steel released preliminary findings about the potential cause of the deadly explosion at U.S. Steel Clairton Coke Works on Monday.