Brush fires burning in Contra Costa County on Saturday morning have consumed 655 acres near Clayton, according to CalFire.
The Marsh Complex Fire was 50 percent contained as of 10:30 a.m. and no injuries have been reported and no structures are threatened, CalFire officials said.
A shelter in place was issued near Clayton and residents there were advised to stay inside and close doors and windows. Smoke from the blaze also prompted air district officials on Saturday morning to issue an air quality advisory for the Bay Area through Sunday.
An estimated 200 firefighters were battling the blazes and aircraft were being used to dump water on the fires, CalFire said. Crews first responded shortly after 3 a.m. to a fire near Marsh Creek Road and Bragdon Way in Clayton.
Cal Fire officials believe six to seven vegetation fires occurred in the area overnight, and the cause of the blazes is under investigation. Authorities have closed Marsh Creek Road between Brentwood and Clayton.
Smoky air from the fires is expected in eastern Contra Costa County, including Antioch, Oakley, Brentwood, Discovery Bay and Pittsburg, according to the Bay Area Air Quality Management District.
Onshore winds are expected to be light and are expected to become stronger throughout the day, the air district said.
Satellite images show that smoke is drifting east and down into the San Joaquin Valley.
If the smell of smoke is present, Bay Area residents should protect their health by avoiding exposure, the air district said. If possible, residents should stay inside with windows and doors closed until smoke levels subside. Real-time air quality readings are available at https://go.usa.gov/xUwyz.