California : Four firefighters have been injured fighting to contain a fast-moving wildfire in northern California that has forced thousands of people to evacuate their homes, but are in stable condition, a fire service spokesman said.

The wildfire, nicknamed the Valley Fire, has spread rapidly to span about 25,000 acres (10,117 hectares) since it erupted on Saturday afternoon in Lake County, north of San Francisco, the California Department of Forestry and Fire Protection (Cal Fire) said on its website. Early on Sunday morning, local media showed footage of several structures ablaze in Middleton, a small community of about 1,500 residents, one of several that were ordered to evacuate by the Lake County authorities on Saturday.

Four firefighters, who had been dropped off by helicopter, suffered second-degree burns as they built containment lines, said Cal Fire spokesman Daniel Berlant. The firefighters were airlifted to UC Davis Medical Center in Sacramento where they were listed in stable condition, Berlant later said on Twitter.

About 100 miles (161 km) to the southeast, the so-called Butte Fire has destroyed 86 homes and 51 outbuildings in rural Amador and Calaveras counties, where it covers an estimated 65,000 acres (26,305 hectares), officials said. It is only 15 percent contained. Thousands of residents in the area were required to evacuate on Friday, and the blaze threatened more than 6,000 structures, officials said. More than 3,800 firefighters were working to contain the fire, which erupted on Wednesday near the former gold mining town of Jackson.