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 has released new details on what investigators believe caused the explosion at the Clairton Coke Works plant that killed 2 people and injured 10 others.