A huge California wildfire has burned into Yosemite National Park, park officials say.
The week-old Rim Fire grew to 424 square kilometres by Friday morning, and had burned 4.4 sq km at the edge of the park by the afternoon.
The blaze has forced scores of tourists to flee during peak season and is threatening thousands of homes.
The BBC reports that more than 2000 firefighters have been tackling the flames in difficult terrain, but that it is just 2% contained.
Reuters reports that the fire is threatening power lines that provide electricity to San Francisco, prompting California Governor Jerry Brown to declare a state of emergency.
The fire has damaged the electrical infrastructure serving the city, and forced the San Francisco Public Utilities Commission to shut down power lines, the governor said in his declaration.
The blaze has shut a stretch of motorway that is one of three entrances to the west side of the park, which receives up to 15,000 visitors a day in the summer.
The Rim Fire is one of 50 major wildfires burning in the western US.
The blaze is centred on Stanislaus National Forest, west of Yosemite, and has so far destroyed two homes and seven outbuildings.
A spokeswoman for the US Forest Service said 4500 homes, hotels, businesses and several campsites are under threat as of Friday, up from 2500 the day before.
Officials have gone door to door in the summer community of Pine Mountain Lake urging people to leave.
