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.

Neighbors of U.S. Steel's Clairton Coke Works and the plants' workers react to the explosion at the plant on Monday that killed two and sent 10 to the hospital.

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