The fire was reported just after 1 p.m. on state Route 94 near Otay Lakes Road about halfway between the communities of Jamul and Dulzura, Cal Fire spokeswoman Roxanne Provaznik said.
Cal Fire sent 15 engines, 3 fire crews, a bulldozer and a water tender to the fire. Two air tankers and two helicopters dropped fire retardant and water on the fire from above.
Crews had the blaze under control in about an hour, but they were expected to remain at the scene for several hours to put out hot spots.
No structures were threatened by the fire.
The cause of the fire is under investigation.