HARRISBURG, Pa. (AP) — The fatal explosion last week at U.S. Steel’s Pittsburgh-area coal-processing plant has revived debate about its future just as the iconic American company was emerging from a long period of uncertainty.

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.

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.