U.S. Steel released preliminary findings about the potential cause of Monday's deadly explosion at U.S. Steel Clairton Coke Works. U.S. Steel spokeswoman Amanda Malkowski said in a statement on Friday that "preliminary indications lead us to believe" that the explosion happened when a gas valve was flushed in preparation for planned maintenance.

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.

United States Steel Corp. said Friday the fatal blast that killed two workers at its Clairton Coke Works facility in Pennsylvania happened when flushing a gas valve in preparation for planned maintenance.