Residents and the fire department attribute the cause of the fire to a downed 12,000-volt power line on the site, but there's some debate about exactly how the line caused the fire.

According to homeowner Richard DeForest, the downed line was a danger to his house, but it didn't start the fire until water from a firefighter's hose was sprayed on the live electrical wire.

The Sunnyvale Department of Public Safety says the house was already on fire when crews arrived, but most of the flames were inside the walls of the house, not visible to people standing outside.

DeForest, who's owned the house since it was built in 1964, said his family was startled from sleep around 5:40 a.m. by a bright flash, a loud pop, a second bright flash and another louder pop.

DeForest's adult son yelled for someone to call 911 because he thought the house was on fire.

At the time, a live and downed power line was sparking on the side of the house. The son was able to get the wire away from the house by using a fire extinguisher.

DeForest said there were no flames when fire crew arrived, but they couldn't move the wire because it was still live.

"It took PG&E 53 minutes to get here," DeForest said. "In the meantime, the fire department wasn't able to do anything."

During the wait, DeForest said, the wire was hit with water from a fire hose and with a "whoosh," the house was in flames. The family had already evacuated the building, so no one was injured.

"We aren't hurt physically, but it'll be awhile until we know the damage to our house," DeForest said while standing in front of his house.

The Sunnyvale Department of Public Safety offers a different statement about the incident.

According to Cpt. Craig Farley, the department of public safety got a call at 5:34 a.m. regarding a downed power line. While en route, they got a second call about a house fire at the same location. Deputy Chief Byron Pipkin said the roof was visibly on fire, and the house itself was beginning to burn from inside because current from the power line was running through the house, frying wiring. Because of the power, the house was also an electrocution hazard.

Pipkin said it's likely small fires were beginning to burn inside the walls of the house. He acknowledged that firefighters were spraying water at the roof of the house, away from the power line, to put flames out. Firemen used short bursts of water to put out flames because a steady stream--had it hit anything electrical--would have electrocuted the people touching the hose.

"Had we known then what we know now, we would not have entered the house," Pipkin said. "We had firemen in the house, and they said they heard a ladder humming when the placed it against the house because it was energized [by electricity]."

At 7:14 a.m., the fire was out but had damaged the garage and second floor of the house.

As crews mopped up, the displaced family gathered across the street at the Congregational Community Church of Sunnyvale. Pastor Gen Heywood said that in addition to coffee and food, the church was trying to help its neighbors get in touch with friends and family.

"We just wanted to find out what they needed, to support them through this," Heywood said. The church was damaged several years ago in a freak Sunnyvale tornado.

"We understand the long haul they're in for; we've been through rebuilding."