PICTURES

California fire threatens San Francisco water and power

The McCain inmate crew out of San Diego struggles to cut a fire line on a steep slope on the Rim Fire near Buck Meadows, California, on Aug 24, 2013. A fast-moving wildfire on the edge of Yosemite National Park has forced the closure of two more area
The McCain inmate crew out of San Diego struggles to cut a fire line on a steep slope on the Rim Fire near Buck Meadows, California, on Aug 24, 2013. A fast-moving wildfire on the edge of Yosemite National Park has forced the closure of two more areas of the park, but an official said on Saturday he was cautiously optimistic that firefighters could halt the advance of flames.  -- FILE PHOTO: REUTERS
A firefighter uses a hose to douse the flames of the Rim Fire on Aug 24, 2013 near Groveland, California. The Rim Fire continues to burn out of control and threatens 4,500 homes outside of Yosemite National Park. -- FILE PHOTO: AFP
A firefighter uses a hose to douse the flames of the Rim Fire on Aug 24, 2013 near Groveland, California. The Rim Fire continues to burn out of control and threatens 4,500 homes outside of Yosemite National Park. -- FILE PHOTO: AFP
Firefighters work to prevent the Rim Fire from jumping Highway 120 near Buck Meadows, California, on Aug 24, 2013. A fast-moving wildfire on the edge of Yosemite National Park has forced the closure of two more areas of the park, but an official said
Firefighters work to prevent the Rim Fire from jumping Highway 120 near Buck Meadows, California, on Aug 24, 2013. A fast-moving wildfire on the edge of Yosemite National Park has forced the closure of two more areas of the park, but an official said on Saturday he was cautiously optimistic that firefighters could halt the advance of flames. -- FILE PHOTO: REUTERS
Firefighters work to prevent the Rim Fire from jumping Highway 120 near Buck Meadows, California, on Aug 24, 2013. A fast-moving wildfire on the edge of Yosemite National Park has forced the closure of two more areas of the park, but an official said
Firefighters work to prevent the Rim Fire from jumping Highway 120 near Buck Meadows, California, on Aug 24, 2013. A fast-moving wildfire on the edge of Yosemite National Park has forced the closure of two more areas of the park, but an official said on Saturday he was cautiously optimistic that firefighters could halt the advance of flames.  -- FILE PHOTO: REUTERS
A Cal Fire firefighter monitors the Rim Fire as it burns through a grove of trees on Aug 25, 2013 near Groveland, California. The Rim Fire continues to burn out of control and threatens 4,500 homes outside of Yosemite National Park. Over 2,000 firefi
A Cal Fire firefighter monitors the Rim Fire as it burns through a grove of trees on Aug 25, 2013 near Groveland, California. The Rim Fire continues to burn out of control and threatens 4,500 homes outside of Yosemite National Park. Over 2,000 firefighters are battling the blaze that has entered a section of Yosemite National Park and is currently 7 per cent contained. -- PHOTO: AFP
Flames from the Rim Fire consume trees on Aug 25, 2013 near Groveland, California. The Rim Fire continues to burn out of control and threatens 4,500 homes outside of Yosemite National Park. Over 2,000 firefighters are battling the blaze that has ente
Flames from the Rim Fire consume trees on Aug 25, 2013 near Groveland, California. The Rim Fire continues to burn out of control and threatens 4,500 homes outside of Yosemite National Park. Over 2,000 firefighters are battling the blaze that has entered a section of Yosemite National Park and is currently 7 per cent contained. -- PHOTO: AFP
Flames from the Rim Fire consume trees on Aug 25, 2013 near Groveland, California. The Rim Fire continues to burn out of control and threatens 4,500 homes outside of Yosemite National Park. Over 2,000 firefighters are battling the blaze that has ente
Flames from the Rim Fire consume trees on Aug 25, 2013 near Groveland, California. The Rim Fire continues to burn out of control and threatens 4,500 homes outside of Yosemite National Park. Over 2,000 firefighters are battling the blaze that has entered a section of Yosemite National Park and is currently 7 per cent contained. -- PHOTO: AFP
US Fish and Wildlife Service firefighter Corey Adams sits on a tree stump as he monitors the Rim Fire on Aug 25, 2013 near Groveland, California. The Rim Fire continues to burn out of control and threatens 4,500 homes outside of Yosemite National Par
US Fish and Wildlife Service firefighter Corey Adams sits on a tree stump as he monitors the Rim Fire on Aug 25, 2013 near Groveland, California. The Rim Fire continues to burn out of control and threatens 4,500 homes outside of Yosemite National Park. Over 2,000 firefighters are battling the blaze that has entered a section of Yosemite National Park and is currently 7 per cent contained. -- PHOTO: AFP
US Forest Service firefighters look at an incident map as they take a break from battling the Rim Fire at Camp Mather on Aug 25, 2013 near Groveland, California. The Rim Fire continues to burn out of control and threatens 4,500 homes outside of Yosem
US Forest Service firefighters look at an incident map as they take a break from battling the Rim Fire at Camp Mather on Aug 25, 2013 near Groveland, California. The Rim Fire continues to burn out of control and threatens 4,500 homes outside of Yosemite National Park. Over 2,000 firefighters are battling the blaze that has entered a section of Yosemite National Park and is currently 7 per cent contained. -- PHOTO: AFP
US Forest Service firefighters take a break from battling the Rim Fire at Camp Mather on Aug 25, 2013 near Groveland, California. The Rim Fire continues to burn out of control and threatens 4,500 homes outside of Yosemite National Park. Over 2,000 fi
US Forest Service firefighters take a break from battling the Rim Fire at Camp Mather on Aug 25, 2013 near Groveland, California. The Rim Fire continues to burn out of control and threatens 4,500 homes outside of Yosemite National Park. Over 2,000 firefighters are battling the blaze that has entered a section of Yosemite National Park and is currently 7 per cent contained. -- PHOTO: AFP
Trees burned by the Rim Fire stand on Aug 25, 2013 in Yosemite National Park, California. The Rim Fire continues to burn out of control and threatens 4,500 homes outside of Yosemite National Park. Over 2,000 firefighters are battling the blaze that h
Trees burned by the Rim Fire stand on Aug 25, 2013 in Yosemite National Park, California. The Rim Fire continues to burn out of control and threatens 4,500 homes outside of Yosemite National Park. Over 2,000 firefighters are battling the blaze that has entered a section of Yosemite National Park and is currently 7 per cent contained. -- PHOTO: AFP
A burned car sits on the side of the road after being consumed by the Rim Fire on Aug 25, 2013 near Groveland, California. The Rim Fire continues to burn out of control and threatens 4,500 homes outside of Yosemite National Park. Over 2,000 firefight
A burned car sits on the side of the road after being consumed by the Rim Fire on Aug 25, 2013 near Groveland, California. The Rim Fire continues to burn out of control and threatens 4,500 homes outside of Yosemite National Park. Over 2,000 firefighters are battling the blaze that has entered a section of Yosemite National Park and is currently 7 per cent contained. -- PHOTO: AFP

LOS ANGELES (AFP) - A raging California wildfire burning on the northern tip of the storied Yosemite National Park now threatens San Francisco's water and electricity supply, officials said Sunday.

The Rim Fire has charred through 54,220ha, growing nearly 3,400ha overnight, according to InciWeb, the online Incident Information System that monitors fires in the western United States.

The fire was just seven per cent contained, InciWeb said, adding that it "remained fairly active overnight in most all divisions," and exhibited "rapid rates of spread, torching and spotting" on its eastern edge.

More than 2,800 firefighters, supported by helicopters and air tankers, are struggling to contain the blaze, which started on Aug 17 from still unknown causes.

Extremely dry conditions due to a prolonged drought, coupled with inaccessible terrain in the affected area, have exacerbated the severity of the incident.

Governor Jerry Brown has declared a state of emergency for San Francisco - which lies some 320km to the west - because the Pacific coast city gets much of its electricity from the region affected by the fire.

The state's firefighting efforts got a boost when California received federal assistance over the weekend to help mobilise the necessary resources.

The San Francisco water and power utility said the city has not so far seen any interruptions in service, though two hydroelectric plants have sustained damage in the fire.

Crews were working on repairing one of the plants, the utility said on its website, and supplemental power supplies in the interim have cost some US$600,000 (S$767,500).

The utility said it also had large reserves of water stored locally, which it will make available if the fire interrupts water delivery.

The fire broke out at Stanislaus National Park, which along with Yosemite is among the state's main natural tourist attractions.

Officials had ordered Tuolumne City and surrounding areas evacuated.

Officials also closed a major interstate highway running through the region.

Mr Brown has also declared a state of emergency in Tuolumne County, allowing him to use additional resources to battle the fire.

Satellite photos earlier showed giant columns of white smoke from the fire drifting far into the neighboring state of Nevada.

The Rim Fire "is expected to continue to exhibit very large fire growth due to extremely dry fuels and inaccessible terrain," Inciweb said.

It said fire crews were using direct attack tactics as well as indirect attacks, which create control lines away from the fire's active edge.