Two coal mines in Wyoming’s Powder River Basin owned by Blackjewel LLC ceased operations on July 1 after United Bank of West Virginia denied the company $20 million in financing to continue operations during bankruptcy proceedings, Blackjewel chief executive officer Jeffery Hoop said.

Eagle Butte and Belle Ayr mines are the fourth- and sixth-largest producing coal mines in the country.

The Casper Star Tribune reported that Blackjewel owes at least $500 million in liabilities, including about $6 million owed to employees, according to court documents. Its financial problems, along with much of the coal sector, come amid increased competition from natural gas and renewables.

Hoop bought the Wyoming coal mines two years ago from Contura Energy. Another of Hoop’s companies in the case, Revelation Energy LLC, operates mines in West Virginia, Kentucky and Virginia.

Blackjewel is the fifth coal producer in Wyoming to file for bankruptcy in recent years. Bristol, Tennessee-based Alpha Natural Resources filed for bankruptcy in 2015, followed by Peabody Energy and Arch Coal in 2016. Westmoreland Coal, which operates the Kemmerer Mine in southwest Wyoming, filed for bankruptcy in October.

In May, Cloud Peak Energy declared bankruptcy. The coal giant owns the Antelope and Cordero Rojo mines in the Powder River Basin.

Even with half of Wyoming’s coal country undergoing consolidation and the other half in bankruptcy proceedings, few experts predicted that the once lucrative Powder River Basin would undergo such a rapid decline, including Rob Godby, professor and director for the University of Wyoming’s Energy Economics and Public Policies Center.

“Up until a few years ago, everyone, including me, knew that thermal electricity from coal was declining, but the Powder River Basin stood as the healthiest of the coal-producing areas,” Godby told the Star Tribune. “People in Wyoming took that for granted.”

A decade ago, Campbell County produced over 360 Mt (400 million st) of coal. Last year, output sank to 256 Mt (283 million st), according to the Wyoming Mining Association.

As the price of coal and demand for the commodity fell, a significant lender for Blackjewel recently pulled out, throwing the company’s already unsteady financial picture into further trouble, according to a company statement.

Still, Hoop’s initial response to the joint filings, which was released prior to the hearing, remained optimistic.

“We are confident that this restructuring will solidify Blackjewel’s position as a significant participant in the U.S. coal market,” he said in a statement. “(The company) will continue as a significant player in the U.S. coal industry for the foreseeable future.”

Gov. Mark Gordon said he was committed to working with the Department of Workforce to provide workforce assistance and the Department of Environmental Quality to ensure appropriate bonding is set.

“This announcement is hardest on the individuals who work at these important mines and their families, and our most immediate concerns lay with them,” Gordon said in a statement. “We are not unprepared for this set of circumstances and are eager to do all we can for the hardworking employees of these mines.”