Cal Fire, San Diego County Sheriff's Department, and the California Highway Patrol are responding to the call of a fire on State Route 79 at Japatul Valley Road.
The fire was reported just after 2 p.m. according to the California Highway Patrol.
Someone called 911 to report flames on the southbound side of the road.
One person who called said a weed trimmer was in use before the fire broke out, according to the sheriff's department.
One home was threatened according to Lt. Amber Baggs who estimated the damage at one acre.