Fire destroyed a workshop and severely damaged an adjacent residence on the 15000 block of Mountain Lily Road in Blue Bell Valley on Sunday afternoon, displacing two adults and three teenage girls.
Cal Fire Capt. Kevin Bowman said no one was home when the fire started.
A neighbor, James Miller, said he saw a shop building burning across the street at the Ralph Souza home and called the fire department.
He said he hadn't talked to the family since and didn't know how they were doing today.
Red Cross Volunteer Coordinator Cathie Peacock said the Red Cross was not called for assistance.
Bowman said the fire started in the shop, which was completely engulfed in flame when firefighters arrived.
It had already spread into an adjacent mobile home and destroyed about 75 percent of that building.
"It went very quickly," he said. "There was one small spot fire, but it was picked up very quickly, and no other homes were endangered."
The fire was reported at 2:17 p.m., contained at 4:10 p.m. and under control by 6:24 p.m., Cal Fire dispatcher Jim DeVoll said.
He had no reports of injuries.
Responding were aircraft from Columbia Air Attack Base, a battalion chief, seven Cal Fire engines, one engine from Tuolumne Fire Protection District and one Tuolumne County engine.
Bowman said the cause of the fire has not yet been determined, but it was not considered suspicious this morning.