Fire officials say a wildfire burning near the Northern California town of Oroville has destroyed 20 homes and seven outbuildings.
The California Department of Forestry and Fire Protection says the so-called Ponderosa blaze about 70 miles north of Sacramento had consumed 3,680 acres or nearly 6 square miles. Flames are threatening 500 homes.
Fire crews increased containment to 30 percent overnight ahead of a statewide heat wave.
But officials say the fire's location in steep and rugged terrain plus hot and dry temperatures are complicating firefighters' efforts.
More firefighters are joining the more than 1,600 already battling the Ponderosa fire.
Investigators have arrested John Ballenger, of Oroville, on suspicion of sparking the flames. The man is accused of "recklessly starting a campfire outside a designated campground and allowing it to escape," Cal Fire said in a statement.
The blaze is one of many wildfires across the U.S. West, including fires in and around California's Yosemite National Park that have closed a popular road into the park prompted evacuations of nearby towns.
