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.

U.S. Steel says it believes a gas valve failure led to the explosion Monday morning at its Clairton Coke Works, in which two workers died and 10 others were injured.