Investigators have determined the fire started either in a corner of a master bedroom near an electric outlet where an iPod and alarm clock were plugged in or near an ashtray outside the house adjacent to the indoor electric outlet, Pforsich said.
There were fresh cigarettes in the ashtray, Pforsich said, but the cause of the fire remains unknown.
Four people from France were visiting the occupants of the house at 7505 Skidmore Lane in unincorporated Sonoma County and were in the home when the fire broke out, Pforsich said.
There was a delay reporting and responding to the fire because the visitors were not familiar with the 9-1-1 emergency system, Pforsich said.
Neighbors also reported the fire, and firefighters arrived around 5:20 p.m.
The fire caused nearly $1 million in damage to the structure and contents in the two-story home, Pforsich said.
Firefighters from Sebastopol, Graton and other districts assisted Gold Ridge firefighters.