A bulldozer puts in a fire line as the Rim Fire burns in the background near the border of Yosemite National Park (Photo: Reuters)
Firefighters in California on Saturday were struggling to contain a giant blaze that threatened thousands of homes and was sweeping into the storied Yosemite National Park.
The so-called Rim Fire doubled in size in just one day, and the 125,600-acre blaze was only five percent contained, according to Inciweb.org, the online Incident Information System that monitors fires in the western United States.
Governor Jerry Brown late Friday 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 fire broke out on 17 August at the Stanislaus National Park, which along with Yosemite is among the state's main natural tourist attractions.
Some 2,000 firefighters battled the blaze with help from tanker planes and helicopters, which dumped flame retardant chemicals from the air. About 4,500 structures are threatened by the wildfire.
Temperatures are mild, but the fire has been fed by the extremely low humidity, dry scrub brush and trees, and gusts of strong wind that pushed the flames into narrow canyons and ridges that are hard for firefighters to reach.
Officials have ordered the small towns of Tuolumne and Ponderosa Hills evacuated. Officials also closed a major interstate highway running through the region.
Earlier, Brown declared a state of emergency in Tuolumne County, allowing him to use additional resources to battle the fire.
Satellite photos show giant columns of white smoke from the fire drifting far into the neighboring state of Nevada.
The Rim Fire "continues to exhibit very large fire growth due to extremely dry fuels and inaccessible terrain," Inciweb said.