The Pennsylvania county where an explosion at a U.S. Steel plant south of Pittsburgh killed two people and injured more than 10 others announced Thursday that it is stepping up air quality monitoring in the area of the sprawling facility that has a troubled environmental record.

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.