Almost 230 square miles in and around California’s Yosemite National Park is being affected by a huge blaze.

Officials said yesterday that the fire was 15% contained after burning for more than a week – up from 2% containment on Friday.

California governor Jerry Brown has declared a state of emergency for San Francisco 150 miles away as the blaze is threatening power lines that bring electricity to the city.

The so-called Rim Fire is also reported to be raining ash on a reservoir that supplies water and hydro-electric power to San Francisco.

Some 2,800 firefighters are tackling the flames in difficult terrain, the BBC reported.

Despite the threat to some 5,000 homes, only a few have been destroyed.

The Foreign & Commonwealth Office said: “There are a number of wildfires currently burning in the western United States including in Idaho and California. Visitors to Yosemite National Park may want to be aware that Highway 120 is closed.”