The fire started Wednesday and has been burning in the dry, rugged land south of Banning, the Los Angeles Times reported.
On Friday, Gov. Jerry Brown declared a state of emergency in Riverside County, making the victims of the Silver fire to be eligible for federal disaster aid.
Cal Fire reported that 48 structures -- 26 homes, 1 commercial and 21 outbuildings -- have been destroyed by the fire and eight others have been damaged.
Ten firefighters and one civilian have been injured due to the fire, Cal Fire said.
The cause of the fire is still under investigation.