Coal stored on the site is believed to have spontaneously combusted, but the company says the fire is being “managed appropriately” and is “fully under control”.

Idemitsu Australia Resources chief operating officer Rod Bridges said the company had contacted the NSW Environment Protection Authority about the incident. 

“Spontaneous combustion within coal stockpiles is naturally occurring, which is why we have in place robust management plans,” he said.

“(The plans) are approved by government to ensure we can appropriately manage these situations when they arise.”

Environmentalist Pat Schultz, who conducts tours of the Leard Forest, said four-wheel drivers had spotted a “steady stream of smoke” coming from the mine.

“If this is happening in mid-winter, with recent rain, obviously it shows what a risk open-cut coal mines are,” she said.

“After the Hazelwood mine fire in Victoria, which burned heavily for weeks, one would expect the mine to be taking these fires seriously.”

The Boggabri Coal Mine, located in the Leard State Forest, has approval to extract up to seven million tonnes of coal a year until 2033.