Update, 9 a.m.
Forward progress of the fire has been stopped, Cal Fire said.
Update, 8:56 a.m.
Authorities have canceled much of the response to the fire as crews continue to make progress on the fire, according to Cal Fire.
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Update, 8:45 a.m.
Firefighters are "making good progress" on the blaze and officials have canceled some of the response crews, Cal Fire said.
Firefighters are responding to a brush fire off Highway 166, Cal Fire said in a tweet.
The fire was reported about 7:45 a.m., according to the California Highway Patrol's incident information page.
The blaze, in the 8200 block of O'Leary Canyon Way, is in a "remote area with challenging access," according to Cal Fire.
As of 8:30 a.m., the fire had burned about a one acre of grass with a slow rate of spread. There is no direct threat to structures, though the fire is near three of them, according to Cal Fire.
This story will be updated as more information becomes available.