ICG spokesman Ira Gamm told International Longwall News nobody was injured in the collapse but the mine would be idled as a precaution.

"ICG Illinois detected a slightly elevated level of carbon monoxide in a previously mined area at its Viper Mine on Saturday, November 3," Gamm said.

"The company investigated the source of the reading and determined that there was a small amount of heated coal."

According to various media reports, federal officials were onsite at Viper on Monday as crews worked to remove a "hot spot" from the mine.

Gamm said the mine could recommence production by midweek and that some of the mine's 255 workers remained on the job during the down time.

"In conjunction with discussions between the state and federal mine safety authorities, production was temporarily halted at the mine while workers restored equipment access to the area and began removing the heated material," he told ILN.

"While coal production is currently suspended, after consultation with the appropriate regulatory authorities, other maintenance work has been allowed to continue."

US Mine Safety and Health Administration spokeswoman Amy Louviere confirmed to ILN the event and the precautionary actions being taken.

"The Viper mine is under a 103k order and is disposing of the hot spot material by loading, spreading it out and cooling/extinguishing with water and rock dust," Louviere said.

Illinois Department of Mines and Minerals director Joe Angleton told the Springfield State Journal Register in an interview Monday that spontaneous combustion is not unusual.

"It was a roof fall ... that puts pressure on existing coal underneath it and creates spontaneous combustion. This never got to the state of an actual fire, but it was smouldering," Angleton said.

The roof section, he added, measured about 100 feet long by 18ft wide; it must be removed from the operation and the area of the fall treated before inspectors can begin work to approve the mine for reopening.