A fire has burned four acres on Mount Diablo in Contra Costa County, Cal Fire officials said Thursday evening.
The fire was reported at 3:30 p.m. close to Summit Road.
The fire has threatened a radio repeater site, which boosts radio signals.
Firefighters are starting to get a handle on it, according to Cal Fire officials. But it's not fully contained, the officials said.
No injuries have been reported and no structures have been reported threatened.