On Monday, it said the idling of longwall face 21-1-7 was due to high levels of carbon monoxide, which was “proof of coal self-heating” and the stoppage was expected to be temporary.

“Southern Kuzbass Coal … experts are working on measures to eliminate [it],” the company said.

“Remote sampling yields prompt information on the gas situation in the production area, which is injected with a nitrogen-based foam.”

It confirmed safe conditions for the mine’s infrastructure, including the transport, ventilation and dewatering systems, as well as its power facilities and roadheaders.

Mechel officials did not indicate a timeline for mining resumption, confirming that the timing would hinge upon the completion of its work to eliminate the condition.

“Suspension of the mine’s longwall face will not cause delay in coal deliveries to customers since there is enough coal at the New-Olzherassk underground mine warehouse to ensure uninterrupted deliveries within the company's existing contractual obligations,” Mechel said.

New-Olzherassk has mined more than 250,000 tons of coal, primarily used for pulverized coal injection production, so far this year.