LOS ANGELES - 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 133,980 acres (54,220 hectares), growing nearly 8,400 acres 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 August 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 200 miles (320 kilometers) 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 mobilize 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.