Hot weather conditions, dry winds and heavy bushes quickly spread the flames which were sparked on Tuesday, Xinhua news agency quoted officials as saying.
The wildfire dubbed as the "Bluecut" fire, spread from five acres to about 9,000 acres within hours.
Video footage showed that at least one house and several other structures were ablaze, the media reported.
The region was under red flag warnings for high fire danger. California Governor Jerry Brown declared a state of emergency in San Bernardino.
Five persons were injured in fire accidents who were transported to hospitals, fire officials tweeted.
Several fires in Southern California this summer have destroyed homes, caused power outages and subjected residents to repeated evacuation orders.
