Air and ground crews are responding to Sierra Pacific Industry's Standard Mill for a stack of logs on fire.
Cal Fire received the call at 11:10 a.m. for a burning log deck on the Tuolumne Road property, according to spokeswoman Lisa Williams.
Two air tankers, a helicopter, bulldozer and nine engines have been dispatched.
It was unknown how many logs were burning or if structures were threatened.
No other information was available.