Spontaneous combustion saw a small fire break out at Rio Tinto’s Bengalla mine this week.
The incident occurred on Tuesday morning in one of the coal seams at the open cut operation.
It understood the blaze was extinguished before lunch.
A spokesman for the company said the burning coal had been buried in the deepest section of the mine to minimise any chance of re-ignition.
When coal is exposed to oxygen its temperature rises and generates heat and in turn promotes further oxidisation, which can cause it to ignite suddenly.