SAN DIEGO -- An intense, smoky fire blamed on spontaneous combustion caused by rags used to apply wood stain broke out Tuesday in the garage of a Mission Valley town house, causing $140,000 in damage but no injuries, authorities said.

The fire at 910 Camino de la Reina in the Mission Gate Complex broke out around 1:30 a.m. and burned for about 30 minutes before it was extinguished by some 50 San Diego Fire-Rescue Department firefighters, said department spokesman Maurice Luque.

The blaze burned with uncommon ferocity.

"When you have it burning in a garage and a car is on fire, it gets pretty intense," Luque said, blaming gasoline and automotive oil for creating a particularly hot fire.

The blaze shattered the windows in the garage and on the second story of the town house, Luque said. He said the flames did not spread to the town house but filled the home with smoke.

The occupants of the town house got out before suffering such injuries as smoke inhalation. Luque credited a woman in her late 60s who was awakened by a fire alarm and woke up her daughter and grandson in time for the three of them to safely rush out with their cocker spaniel.

Fire investigators determined the blaze resulted from spontaneous combustion caused by rags being used to stain hardwood floors, Luque said.

He said the fire caused $140,000 in damage -- $85,000 in structural damage, $50,000 in damage to content, and $5,000 representing the loss of the car that had been in the garage.