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

A gas valve failure caused the explosion at Clairton Coke Works on Monday morning that killed two people, U.S. Steel said Friday. Why it matters: The massive Mon Valley facility — one of the largest coke plants in the world — has a long history of environmental and safety violations.

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.