ORINDA -- Fire crews are responding to a grass fire near Grizzly Peak Boulevard, on the southeastern end of Tilden Park, officials said Monday.

The fire was reported about 9:30 p.m. and is spreading at a moderate pace, according to fire dispatch. The fire was originally reported to be about one acre in size, but the area is filled with heavy vegetation that could act as fuel for quick spread, officials said.

Crews from the Contra Costa County Fire Protection District, CalFire, Alameda County Fire, East Bay Regional Parks and the Moraga Orinda Fire Department are on the scene.

Check back for updates.