Cal Fire freighters are working to extinguish a 4 acre blaze near Copperopolis.
The fire, on the 3000 block of Paint Road, was reported at 10:46 a.m.
As of 12:30 p.m., there was no containment.
The cause remains under investigation.
A total of 64 personnel were assigned to the fire. Equipment included eight bulldozers, one water tender, one air attack plane, one tanker, two helicopters.