The U.S. Chemical Safety Board investigating the Aug. 11 explosion at Clairton Coke Works said it is focusing on the metallurgic analysis of the failed cast iron valve, U.S. Steel’s use of cast iron piping for coke oven gas, and its policies, procedures and safety management systems.

The federal agency issued preliminary findings on Monday, which U.S. Steel said aligned with its own investigation.

Two U.S. Steel employees, Steven Menefee, 52, and Timothy Quinn, 39, died in the explosion.

Five others were seriously injured, including an employee from Veolia Water North America Operating Services, who was escorting an Allegheny County Health Department inspector performing an air quality check. One of U.S. Steel’s workers was trapped under debris for about four hours after the explosion b

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