Cal Fire spokeswoman Pam Temmermand said the fire is at 40 to 50 acres as of 2:30 p.m. and a mix of residential and outbuilding structures, like sheds and barns, are involved.
About 75 firefighters are responding to the blaze, Temmermand said.
Three outbuildings were destroyed.
San Jose firefighters are providing mutual aid and the fire has been contained.