An idling classic car started a fire at a house on Moon Mountain Road on Tuesday which closed a section of Highway 12 while firefighters worked to contain the blaze.

The fire was reported at 1:06 p.m. in the two-story Agua Caliente home and was brought under control within about 45 minutes, according to Division Chief Spencer Andreis of Sonoma Valley Fire and Rescue.

Andreis said the likely cause of the fire was a classic car, believed to be a Cadillac, that was idling in the garage.

"It appears somehow the engine caught fire," he said. "By the time we got there, the garage was fully involved. Most of the second floor was a total loss."

He said the family made arrangements for a place to stay.

Andreis estimated the damaged to be more than $100,000.

Glen Elen, Cal Fire, Schell Vista, Eldridge, Kenwood and Rincon Valley all responded to the blaze.

Staff Writer Jamie Hansen contributed to this report.