Grass Fire Burning On San Bruno Mountain Near Highway 101: Photos

SAN MATEO COUNTY, CA — A small, slow-moving grass fire around 10 acres was burning on the east side of San Bruno Mountain on Friday morning, according to officials.

It was 80 percent contained as of noon.

The fire broke out around 4:45 a.m., and the cause is under investigation, according to Cal Fire CZU. No structures were threatened so far.

It began as four to five acre fire, but was "holding at an estimated eight to 10 acres" shortly after 7:30 a.m., according to Cal Fire CZU.

Firefighters were making "good progress" on the blaze. A bulldozer was being used to cut a fire line.

Cal Fire CZU said before 8 a.m. that fire activity "was increasing" and additional resources were on the way.

Roads near Airport Boulevard and Bayshore Road in Brisbane was closed as firefighters and police officers responded.

The fire was slightly visible from Highway 101 around 7 a.m. as the fog began to lift.

Fire engines were parked near the Mandalay Bay neighborhood in South San Francisco as a precaution, according to Cal Fire CZU.