An explosion at a U.S. Steel plant south of Pittsburgh killed two people and injured more than 10 others. The CEO has vowed to find out what caused Monday’s blast while the workers’ union says it will make sure there’s a thorough investigation.

Steelworkers at US Steel’s Clairton Coke Works have come forward to expose the long-standing and deadly safety hazards that preceded Monday’s explosion, which killed Timothy Quinn and Steven Menefee and injured ten others.

Two people were killed and 10 others were injured in an explosion at the U.S. Steel Clairton Coke Works plant on Monday.