GRAND JUNCTION, Colo. (AP) — Conservation groups have filed a federal lawsuit against St. Louis-based Arch Coal over methane and other toxic air emissions at the company's West Elk Mine in Colorado's North Fork Valley.

WildEarth Guardians, the Sierra Club, the Center for Biological Diversity and High County Conservation Advocates filed the suit this week in U.S. District Court in Denver, The Daily Sentinel reports.

The West Elk Mine, near the unincorporated community of Somerset in Gunnison County, is Colorado's largest coal mine. It produced more than 4 million tons of coal in 2019, according...