A massive wildfire has crossed into California's Yosemite National Park after burning for nearly a week on its edges, and firefighters have barely begun to contain it.
The Yosemite Valley, the part of the park frequented by tourists and known around the world for such iconic sights as the Half Dome and El Capitan rock formations and Yosemite falls, remained open, clear of smoke and free from other signs of the fire that remained about 30 kilometres away.
But the blaze of nearly 518 square kilometres was reverberating around the region. The fire was 5 per cent contained and more than 2,000 firefighters were on the lines.
California Gov. Jerry Brown declared an emergency late Friday for San Francisco 240 kilometres away because of the threat the fire posed to utility transmission to the city, and caused smoke warnings and event cancellations in Nevada as smoke blew over the Sierra Nevada and across state lines.
The fire had established a foothold in Yosemite, with at least 44 square kilometres burning inside the park's broad borders, in a remote area near Lake Eleanor where backpackers seek summer solace.
'No visitor servies are being affected'
Park spokeswoman Kari Cobb said that the park had stopped issuing backcountry permits to backpackers and had warned those who already had them to stay out of the area.
She emphasized that the skies over Yosemite Valley were "crystal clear," however.
"Right now there are no closures, and no visitor services are being affected in the park," Cobb said. "We just have to take one day at a time."
The blaze did, however, pose a threat to the lines and stations that pipe power to the city of San Francisco. The city gets 85 percent of its water from the Yosemite-area Hetch Hetchy reservoir that is about 6 kilometres from the fire, though that had yet to be affected. But it was forced to shut down two of its three hydroelectric power stations in the area.
The city has so far been able to buy power on the open market and use existing supplies, but further disruptions or damage could have an effect, according to city power officials and the governor's statement.
The declaration frees funding and resources to help the city and makes it eligible for more federal funds to help with power shortages and outages or water problems.
The fire continued to grow in several directions, although "most of the fire activity is pushing to the east right into Yosemite," said Daniel Berlant, spokesman for the California Department of Forestry and Fire Protection.
In Nevada, the smoke forced officials in several counties to cancel outdoor school activities and issue health advisories, especially for people with respiratory problems.
The fire was threatening about 5,500 residences, according to the U.S. Forest Service. The blaze has destroyed four homes and 12 outbuildings in several different areas.