Crews are fighting a fire on the grounds of Camp Pendleton that had burned about 75 acres as of 5:15 p.m. The fire broke out shortly before 4:30 p.m.
Base officials said the fire, which is not part of a controlled burn, has the potential to burn about 300 acres.
The fire is 20 percent contained.
The blaze was apparently sparked by training exercises and is spreading in the eastern reaches of the base, according to Gunnery Sgt. Paul McQuigg, a spokesman for the base.
No structures were threatened, he said.
Ground and airborne crews were fighting the flames, including two Cal Fire air tankers.
