The deadly explosion at Clairton Coke Works near Pittsburgh occurred when a gas valve was flushed before planned maintenance, U.S. Steel said in preliminary findings.

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 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.