Two workers in Martinez were taken to the hospital Wednesday after a chemical leak at a gasoline production unit at Tesoro's Golden Eagle refinery in Martinez.
Company spokeswoman Tina Barbee said the workers were taken to the University of California Davis Medical Center after they were exposed to the leak about 2:40 a.m.
A community warning system was sounded and the production unit was shut down, she said.
The Contra Costa County Health Department, law enforcement and fire departments, and the San Francisco Bay Area Air Quality Management District were notified.
The cause of the incident is under investigation.