Firefighters responded to the blaze around 10:08 a.m. Four engines, two ladder trucks and 26 personnel from the San Ramon Valley Fire Protection District arrived at the scene and had the fire under control at 10:31 a.m.
The homeowner heard a "pop" in her home and left and called the fire district, said Battalion Chief Mike Brown. When firefighters arrived, the fire has spread extensively throughout the house.
Firefighters doused the fire with water on the outside of the house and then went inside to attack the flames.
The blaze caused heavy damage in the garage and to the kitchen, and smoke and heat caused destruction throughout the house.
Fire experts are still investigating the cause of the disaster, said district officials. "We are working on it," said Brown.
SRV Fire Protection District firefighters were called upon a few hours later to extinguish a six-acre grassfire off Wittenham Court in San Ramon, which was reported at 12:40 p.m. Eight engines responded, with 25 personnel, six who were off-duty.
The grass fire was begun by the cutting of a pipe that caused sparks to ignite the dry grass, said Brown.