According to a US Securities and Exchange Commission filing made public by the company this week, the methane was detected by a US Mine Safety and Health Administration official at the face of an idle entry of the mine at about 9.30am local time December 13.

“No miners were working and no mining equipment was located in the face of the idle entry at the time of the order's issuance,” the company said.

Alliance subsidiary White County Coal, which operates the mine, adjusted the ventilation controls in the entry and diluted the gas.

No injuries or incidents were reported as a result of the condition, and MSHA terminated the order an hour after it was written.

“WCC is presently reviewing the matter to determine if it will seek judicial review of MSHA's decision to issue the order,” the company said.

Alliance did not issue further public statement on the order.

Pattiki received a second order on October 13 for a water-related imminent danger that it voluntarily reported to regulators.

“MSHA confirmed the findings of WCC's own mine examiners, who observed evidence of water around certain 120 psi seals,” officials reported.

“The seals are used to separate older, previously mined areas from the areas actively being mined for coal. Prior to the issuance of the imminent danger order, WCC already had removed all miners from the underground mine and had begun efforts to pump excess water away from the seals.”

Alliance confirmed that no injuries occurred. The order was terminated October 17 and normal mining operations resumed at that point.

“WCC is reviewing MSHA's order and may seek judicial review of its issuance,” Alliance said at the time.

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.