A huge wildfire near Yosemite National Park in California has forced scores of tourists to flee during peak season and is threatening thousands of homes.

The week-old Rim Fire more than tripled in size on Thursday and now spans at least 84 square miles (217 sq km).

More than 1,300 firefighters have been tackling the blaze in difficult terrain but have contained only 1% of it.

California's governor has declared a state of emergency because of the fire, one of 50 burning in the western US.

The blaze has not reached Yosemite itself, which remains open, officials say.

But it 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.

'Busy' park
The blaze is centred on Stanislaus National Forest, west of Yosemite, and has so far destroyed two homes and seven outbuildings.

But the authorities are warning that at least 2,500 homes, hotels, businesses and several campsites are under threat.

Officials have gone door-to-door in the summer community of Pine Mountain Lake urging people to leave.

Local residents said the area, normally teeming with tourists, is now empty.

"This fire, it's killing our financial picture," restaurant owner Corinna Loh told the Associated Press. "This is our high season and it has gone to nothing, we're really hurting."

"We've got a monster on our hands," Lee Bentley of the US Forest Service told CBS News.

"This fire is making its own weather. It's going every which direction. This is one of the worst I've ever been on. I've been doing it for quite a few years."

The area's steep hills and rugged terrain are hampering firefighters' efforts, officials say. Extra firefighters are due to arrive on Friday.

Despite the fire's proximity to Yosemite, spokesman Scott Gediman says the park is clear of smoke, and all accommodation and attractions are open.

"The fire is totally outside the park," he told the AP. "The park's very busy, people are here. There's no reason that they should not come."

Meanwhile, five wildfires in Yellowstone National Park have scorched about 18 square miles of mostly remote areas.