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Cheyenne, Wyo. • The beginning of bankruptcy proceedings for the nation's second-biggest coal company cast another dark cloud over the economy of Wyoming and other states in the top coal-producing region.

St. Louis-based Arch Coal Inc. says its Chapter 11 filing won't affect employee pay or benefits while the company reorganizes its debt. The company says the bankruptcy process will not result in mine closures or layoffs, and coal deliveries will continue without interruption.

Arch was Utah's largest coal-mine operator until the summer of 2013, when it sold Canyon Fuel Co. and its Sufco, Dugout Canyon and Skyline mines to Bowie Resources for $435 million.

Longer-term, the company isn't ruling out closures and layoffs, depending on the coal market.

Two Arch mines in Wyoming and one in Colorado together employ 2,100 people. Arch's Black Thunder mine in Wyoming is the world's biggest coal-mining complex.

Wyoming mines supply about 40 percent of the nation's coal. Low natural-gas prices drove U.S. coal production to the lowest levels in three decades last year.