The Butte County Sheriff's office said the victims were found dead in vehicles that had been burned by the Camp Fire that left a trail of destruction in its path.
Dozens of other people were reported missing.
The vehicles with the deceased were found close to each other and near a roadway that leads out of Paradise, California, which has been largely consumed by fire since Thursday. A state fire official said the Camp Fire had almost quadrupled overnight to 285 square kilometers.
On Friday morning, gruesomely burned cars littered the side of the road.
Speaking at a news conference with cooperating agencies, officials addressed the public from Silver County Fairgrounds Friday evening.
"Fire is burning out of control, heading into populated areas of Malibu".
A fast-moving wildfire advanced to the outskirts of the Northern California city of Chico early on Friday, forcing thousands to flee after it left the nearby town of Paradise in ruins.
Butte County supervisor Doug Teeter said authorities used a bulldozer to push abandoned cars out the way to reach Feather River Hospital and evacuate patients as flames engulfed its old wing and the roof of the emergency department. One of them is just 5 per cent contained.
About 20 of the same deputies who were helping to find and rescue people lost their own homes, Sheriff Kory Honea said. "We're kind of all shaking right now".
Areas of northern and southern California continue to be evacuated as the fiery whirlwind of the the Camp Fire struck today.
Some of the first responders who rushed to the scene of the second mass shooting in less than two weeks in the United States were also helping out with fire-related duties.
The massive blaze that hit Paradise spread north Friday, prompting officials to order the evacuation of Stirling City and Inskip, two communities north of Paradise along the Sierra Nevada foothills. Los Angeles County Fire Chief Daryl Osby said a "significant number" of homes had been destroyed by the flames but that an accurate count could not yet be made. At one point, the Camp Fire was consuming 80 football fields worth of land per minute, fueled by winds of up to 50 mph.
The Woolsey Fire broke out on Thursday and quickly jumped the 101 Freeway in several places.
That prompted residents to abandon their vehicles and run from the flames, carrying children and pets, officials said. "We pretty much had enough time to get the dogs in the trunk". He worked so long in the flames and smoke that he needed to use oxygen Thursday night at his home, but he refused to leave.
Malibu and Calabasas, west of Los Angeles, are home to hundreds of celebrities and entertainment executives attracted by ocean views, rolling hills and large, secluded estates. "Just landed back home and had one hour to pack up and evacuate our home". On Instagram she urged people to "pray for Calabasas".