Associated Press reported PinnOak had sought permission to re-enter the mine to adjust a regulator, which would allow more air into the affected area, but the request was denied by MSHA and the state Office of Miners' Safety, Health and Training.

Regulators had expressed concerns that gas levels in the mine continued to be at dangerous levels.

"We are concerned about hydrogen, methane and carbon monoxide -- and the relationship of those gases to one another," William Crocco, acting manager of the federal Mine Safety and Health Administration's District 4 office in Mount Hope, told Associated Press.

Mining regulators plan to continue monitoring air quality in the mine for several weeks.

As previously reported, the mine was idled in early September following a ventilation disruption most likely caused by a lightning strike. PinnOak Resources had employed Polish technology from the Central Mines Rescue Station in Bytom to put out the mine fire with the Polish GAG jet engine used from October 1 through to October 19 and operated by Polish technicians on a 24/7 schedule. The purchase and operation of the equipment was handled by US-based international mining services company, MICON.

"Based on all of the information we have been provided we believe the disruption caused by the lightning is over. However, even though Pinnacle management is working diligently with government officials and the UMWA to safely reopen the mine, it is uncertain at this point when they will be allowed to do so," said CEO Nick Carter.

Pinnacle had previously revised it fourth quarter earnings outlook.