Company spokesman Jeff Gillenwater told Associated Press the layoffs bring the total of furloughed mines across the company to 800 in the past year.

He was not sure if more would follow.

"That's all driven through the fact that market conditions are tight and demand is down," he told the wire service.

"It's challenging right now to the coal market."

A pipeline rupture at Sidney Coal's preparation plant last April sent 135,000 tonnes of coal slurry into the Big Sandy River.