U.S. Steel last year settled a lawsuit brought by environmental groups over emissions that stemmed from the 2018 Clairton plant fire. The settlement with the groups and the county included $19.5 million in coke-oven upgrades and $17.5 million in other plant improvements.

The mill, which is part of the recent merger between U.S. Steel and Nippon Steel, has faced scrutiny from federal and local regulators.

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.