In a US Securities and Exchange Commission filing, the Virginia-based producer said the incident occurred at the Spartan Mining Road Fork No.15 operation near Pineville.

Withdrawal of miners was ordered, though the required foremen did remain underground to locate the source of the smoke.

“A slipping conveyor belt was promptly identified as the source and repaired,” officials said in documentation.

“No fire was discovered, and all air readings indicated that no fire or combustion had occurred in the mine.”

Alpha subsequently terminated the order from the US Mine Safety and Health Administration on May 21.

No injuries were reported as a result of the condition, and Alpha did not release any further comment on the incident.

Imminent danger orders are issued by MSHA under section 107(a) of the Federal Mine Safety and Health Act, also known as the Mine Act.

Section 1503 of the Dodd-Frank Wall Street and Consumer Protection Act, amended last July, now requires disclosure of all imminent danger incidents as part of new reporting requirements regarding mine safety.

Alpha took over Spartan Mining as part of its purchase of Massey Energy last year.

A conveyor belt fire at another Massey mine, Aracoma, killed two miners in 2006. The victims, unable to locate their crew or find an escapeway, died from smoke inhalation.