The car burned in the 4800 block of Polk Avenue about 2:40 a.m., according to San Diego police and the San Diego Fire-Rescue Department. San Diego Fire-Rescue Department spokesman Lee Swanson said no cause had been established, but it could have been electrical.
Two earlier fires were believed to have been deliberately set, San Diego police Sgt. Ray Battrick said.
One fire burned the side of a house in the 4200 block of Chamoune Avenue, and a mattress was set on fire in the nearby 4200 block of 46th Street, he said.
Battrick said two suspects, whose names were withheld pending booking, were detained.