State attorney general Kathleen Kane confirmed that charges against Donald Adams, 51, also include one count of recklessly endangering another person and one count of unlawful conduct from allegations that he was smoking at the Emerald mine in Greene County.

The charges are criminal violations of the Bituminous Coal Mine Act.

According to the criminal complaint, miners working underground in the Emerald operation smelled heavy cigarette smoke toward the end of one of their shifts and discovered a green water bottle and a burned cigarette near the air lock doors.

After collecting the water bottle and cigarette, the workers exited the area’s air lock doors. They immediately smelled cigarette smoke and found a seated Adams.

Kane confirmed that there were 117 miners working underground at Emerald when the incident occurred. Also, methane gas was present in the mine at the time.

“The dangers of smoking in an underground mine are considerable,” chief deputy attorney general Glenn Parno said.

“The Environmental Crimes Section is committed to vigorously pursuing criminal violations of the commonwealth's mining laws, especially violations that jeopardize the health and safety of mine workers.”

Adams, who has been preliminarily arraigned before Waynesburg magisterial district justice D Glenn Bates, is free after posting $US50,000 unsecured bail.

His preliminary hearing has been scheduled for February 14, 2013. No case number was available.

The accused will be prosecuted by deputy attorney general Amy Carnicella of the state attorney general's Environmental Crimes Section.

The Pennsylvania Department of Environmental Protection assisted with the investigation.