Fire fighters battled a blaze at the BHP Billiton West Cliff Colliery coal wash near Appin for more than an hour on Sunday night.
About 30 fire fighters from Fire and Rescue NSW and Southern Highlands Rural Fire Service were called to the incident at 7.25pm.
Southern Highlands RFS team district superintendent Martin Surrey said crews arrived to find two stand alone storage containers well alight.
An electrical fault is believed to have started the blaze, he said.
Supt Surrey said colliery staff had been able to isolate the power and call emergency services.
“It wasn’t too difficult to isolate the fires and put it out,” he said.
“Getting water to the site was the main priority for our vehicles but once they established lines it was quite simple to put out.”
Supt Surrey said no one was injured in the blaze and there had been little risk of the fire spreading.