Two Fresno County deputies and a police officer were shot by a man who then barricaded himself inside a house and continued to fire on law enforcement officials.
A neighbor said he heard what sounded like hundreds of shots.
Sheriff's spokesman Chris Curtice had no further details about the ongoing standoff. It was unclear if any other people were inside the home in the community of Minkler in eastern Fresno County.
The injured officers were shot during an unspecified investigation in a rural part of Central California. Two were deputies with the Fresno County Sheriff's Department. The other was a police officer from Reedley.
Their conditions were unknown. They were taken to a hospital.
The shooter has not been identified.