According to a May 31 filing with the US Securities and Exchange Commission, Massey said its Mammoth Coal subsidiary received the order from the US Mine Safety and Health Administration on May 25 for methane and oxygen levels at the Mammoth No. 2 Gas operation.

The mine was not producing coal at the time, as a prior roof fall necessitated ventilation adjustments underground before resuming operations.

“Before these ventilation changes could be completed, the company and MSHA personnel detected a methane reading of 5% with 19.1% oxygen at the mine,” the company said in the filing.

“An imminent danger order was entered and all personnel were removed from the affected area.”

No injuries were reported as a result of the hazard and Massey terminated the order by adjusting the ventilation controls and clearing the methane from the area.

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, requires disclosure of all imminent danger incidents as part of new reporting requirements regarding mine safety.

Prior to its acquisition by Alpha, Massey had a total of 47 mines in southern West Virginia, eastern Kentucky, southwest Virginia and Tennessee and held 2.3 billion tons of proven and probable coal reserves.

The internal investigation into the Upper Big Branch explosion last April is still ongoing, as is MSHA’s probe. Massey held a safety stand down late last year to focus on potential hazards at all of its mines and facilities.