A vegetation fire that started Friday morning near the picnic area in the San Bruno Mountain State and County Park in northern San Mateo County near Daly City was contained to 6.1 acres, North County Fire Authority officials said.
Crews responding shortly after 10 a.m. to the fire found it burning at a slow speed in heavy brush.
Additional companies, including Cal Fire hand crews and a helicopter, were called and were able to limit the blaze.
There were no injuries and no structures threatened, officials said.
Personnel will monitor the scene overnight and check for hot spots.
The location is under the jurisdiction of Cal Fire, which will investigate the cause.