A "spot fire" was reported at about 3:15 p.m., and was burning at the top of the hill near the hang-glider launch area, according Battalion Chief Robert Mercado.
Three city engines responded to the scene, where a 10-by-10-foot fire was burning in light vegetation with a small amount of wind.
"It wasn't spreading very rapidly,"Mercado said.
Bystanders at the scene helped douse the fire as firefighters made their way to the hillside location, and fire crews mopped up the area using hand tools.
An investigator was on scene looking for the cause of the fire, but "it looks like it's going to be accidental in nature," Mercado said.
There aren't any significant ignition sources close to the fire, and many people were seen walking through the area Thursday afternoon, he said.
A county helicopter was called "as a precautionary measure" because of difficult access to the fire's location, but was canceled, Mercado said.