About a dozen other structures are threatened. Crews hope to have it contained by nightfall.
Fire officials say it started just after noon off Highway 12, in an area between Fairfield and Suisun City known as the Potrero Hills.
Grizzly Island has been evacuated and school children who were on a field trip at Rush Ranch have been told to leave.
People have been reporting the smell of smoke from that fire in many parts of the Bay Area, including the East Bay and San Francisco. It's also been creating haze in the sky in Oakland.
Because of the smoke, the Bay Area Air Quality Management is issuing a smoke advisory to Bay Area residents.
Smoke from this fire has been observed moving southwest into the Bay Area and may impact parts of San Francisco, the East Bay, and Peninsula.
Bay Area residents in these regions are advised to:
* Reduce exposure to smoky air by remaining indoors with windows and doors closed
* Set air conditioning units and car vent systems to re-circulate
* If air smells of smoke, limit outdoor activities to avoid unnecessary exposure
* If you have asthma or other lung disease, make sure you follow your doctor's directions about taking your medicines and following your asthma management plan. Call your doctor if your symptoms worsen.
* If you have heart or lung disease, if you are an older adult, or if you have children, talk with your doctor about whether and when you should leave the area.
* Go to www.baaqmd.gov or www.sparetheair.org to check real-time air quality
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