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

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.

Brian Doyle remembers the explosion that hurled him to the coke plant’s floor — but little else from that day. It was a Wednesday — July 14, 2010 — and Doyle, a steamfitters union member and contractor for Power Piping,