CAMPO, Calif. -- A 100-acre brush fire Sunday in a rural area northeast of Campo prompted some area residents to be asked to leave their homes, according to Cal Fire and the San Diego County Sheriff's Department.

The brush fire was reported in the vicinity of Old Highway 80 and Miller Valley Road about 2:10 p.m. and grew to scorch 12 acres by about 3 p.m., according to Capt. Mike Mohler of Cal Fire.

The fire was spreading at a rapid rate and had grown to 100 acres shortly after 5:15 p.m., according to Cal Fire.

Residents in the 37000 block of Old Highway 80 and those on Church and Crestwood roads near the fire were asked to head east from the area, according to a sheriff's department dispatcher. Sheriff's officials were working to initiate a reverse 911 system to notify those in the affected area, she said.

Those in in need of a safe place to go could head to the parking lot of the Golden Acre Casino at 1800 Golden Acorn Way, the dispatcher said.

About 50 firefighters were working to gain control of the blaze and were using two air tankers, a helicopter and an air attack plane, Mohler said.

San Diego Gas and Electric was called out because the fire could affect power lines in the area, according to Cal Fire.

The cause of the fire remained under investigation and no injuries were reported, Mohler said.

Smoke was visible on Interstate 8 near the Crestwood Road off-ramp, according to the California Highway Patrol, who said the roadway at Old Highway 80 at Crestwood Road was blocked.