San Francisco emergency as Yosemite fire rages

A huge fire in and around California’s Yosemite National Park has continued to spread and now covers almost 600 sq km, officials say.

California Governor Jerry Brown has declared a state of emergency for San Francisco 220km away.

The fire is now raining ash on a key reservoir that supplies water and hydroelectric power to San Francisco.

The blaze is also threatening thousands of homes and some of California’s renowned giant sequoia trees.

Strong winds are making the fires more difficult to control. Some 2,800 firefighters are tackling the flames in difficult terrain.

"It’s a very difficult firefight,” said Daniel Berlant of the California Department of Forestry and Fire Protection.

The blaze began on August 17 but the cause is still unknown