CHARLESTON (AP) — The federal Mine Safety and Health Administration has issued a dozen citations and enforcement orders at an Alpha Natural Resources mine where a conveyor belt burned.

The Charleston Gazette reported that among its findings, MSHA accuses management at Alpha’s Road Fork No. 51 mine in Wyoming County of failing to evacuate when thick smoke was discovered.

MSHA spokeswoman Amy Louviere has said the mine was cited for serious and substantial violations.

The incident prompted MSHA to undertake a one-day inspection blitz at 43 former Massey Energy operations last week in West Virginia, Virginia and Kentucky. Virginia-based Alpha bought Massey’s operations last year for $7.1 billion.

MSHA filed an imminent danger order at the Road Fork mine May 18. MSHA evacuated all employees, except for a few foremen. No one was injured, but the order wasn’t lifted for three days.

MSHA said inspectors determined management did not evacuate the mine as it was attempting to locate the source of the smoke.

“The operator has engaged in aggravated conduct constituting more than ordinary negligence because thick smoke was verified, the source of the smoke was not known, mines were underground and the extent of the source could not be determined to allow miners to remain underground safely,” MSHA said. “This violation is an unwarrantable failure to comply with a mandatory standard.

Alpha spokesman Ted Pile has said workers handled the Road Fork incident properly and it wasn’t life-threatening. Pile didn’t immediately respond to a request for comment Thursday.

Among other problems cited by MSHA inspectors at the mine include a failure to maintain or examine smoke detection equipment and conveyor belts, and allowing combustible coal dust to accumulate in working areas.

MSHA hasn’t release the number of overall citations and orders issued in the blitz, but Louviere has said none were as serious as those at Road Fork.