The agency says the incident broke out around 3:15 p.m. on Wednesday off West Corral Hollow Road in Carnegie State Park, which is a popular site for offroading. The fire is burning southwest of Tracy.
The fire remains at 283 acres burned, but containment has increased to 75 percent, fire officials said.
Firefighters were on the ground and helicopters dropped water and retardant on Wednesday.
Crews are calling this the Hollow Fire.
Officials said firefighters will be on scene Thursday improving fire lines and mopping up.
Cal Fire says it is 50 percent contained.
Stay with ABC7 News for the latest details on this developing story.