The fire is burning near Kirker Pass Road and Nortonville Road near Clayton and Pittsburg.
CAL FIRE said the blaze started from a car fire and had a "moderate rate" of spread, but forward progress has been stopped.
Kirker Pass Road is closed from Hess Road in Concord to Buchanan Road in Pittsburg, the fire department said.
CAL FIRE said crews will remain at the scene for two to three hours.
#KirkerFire on Kirker Pass Rd and Nortonville Rd is 50% contained with forward progress stopped. An aggressive response from @ContraCostaFire and CAL FIRE stopped this fire at 35 acres. Firefighters will remain at scene for the next 2-3 hours. pic.twitter.com/9nz3HUSNc6— CAL FIRE SCU (@calfireSCU) July 4, 2021
Firefighters are at scene of a vegetation fire on Kirker Pass Road and Nortonville Road in the Clayton area. Fire is reported at 3-4 acres, grass, rapid rate, started from a vehicle fire. #KirkerFire @ContraCostaFire pic.twitter.com/3pB0aoWR0y— CAL FIRE SCU (@calfireSCU) July 4, 2021
CAL FIRE Air Attack is at scene and is reporting 20-25 acres, moderate rate of spread with a potential of 50-100 acres.— CAL FIRE SCU (@calfireSCU) July 4, 2021
This is developing, check back for updates