Illegal campfire sparked California wildfire, official says

A deadly wildfire that continues to spread near California's scenic Big Sur was started by an illegal camp fire, a fire official said Tuesday.

Fire information officer Deborah McClain said investigators determined the blaze started July 22 in a day camping area of Garapata Park where campfires are prohibited.

• Fires fuelled by warming climate are increasing
• Q&AWildfires: The science of how they spread and how they're stopped

Officials are still trying to determine who started the fire and are asking for information from campers who were in the area before the massive blaze charred more than 178 square kilometres and destroyed 57 homes, McClain said.

"They have determined the place of origin and the cause and they are still trying to find who and why," she said. "They don't know if it was intentionally set or not, that part is still ongoing."

A bulldozer operator working the fire lines was killed last week in a rollover accident in steep, forested ridges.

More than 5,400 firefighters from across California are fighting the blaze that is threatening 2,000 structures. It was 25 per cent contained Tuesday.

All California state parks in the area were closed until further notice.

Farther north, a quicklyspreading grass fire near Lake Berryessa prompted the evacuation of an RV and tent camping site off of Highway 128 in Yolo County. The blaze started Tuesday afternoon and grew to six square kilometres in hours.

In California's Central Valley, crews got a lot more control over a stubborn wildfire that has destroyed three homes and is threatening another 400 northeast of Fresno. It has burned two other buildings.

Authorities said firefighters increased containment to 60 per cent.

The California Department of Forestry and Fire Protection said about 300 people were under evacuation orders from homes just outside Sierra National Forest.

The eight-square-kilometreblaze started Saturday and quickly spread through steep, rugged terrain covered with dry vegetation and dead trees.

• ANALYSIS |As climate change claims heat up, insurance industry says we need to adapt: Don Pittis