HAILEY - Fire crews on Saturday faced another challenging day battling a rapidly growing wildfire burning closer to two posh central Idaho resort communities, while other blazes in the West charred homes and devoured dry grass and brush.

In northern Utah, about 10 homes were destroyed when a wildfire raced through the community of Willow Springs late Friday, jumping a state highway and fire lines, authorities said.

As of midday Saturday, the Patch Springs Fire had burned more than 50 square miles. It was 20 percent contained.

In Idaho, the Beaver Creek Fire grew by 15 square miles late Friday and early Saturday, to 144 square miles. Overnight, flames moved closer to homes and subdivisions in the mountains west and north of the communities of Hailey and Ketchum and the Sun Valley Resort.

So far, authorities have issued mandatory evacuations for 1,600 residences in the valley, which serves as a vacation getaway for celebrities like Arnold Schwarzenegger and Tom Hanks.

The blaze was started by lightning Aug. 7. It expanded significantly Friday, burning through tinder-dry brush and timber in the mountains west of the towns. Efforts Saturday were focused on protecting homes and structures in the gulches and foothills just west of Hailey and Ketchum.

Crews also planned to target erratic, wind-driven fire growth in one area north of Ketchum and two locations west of Hailey.

Heavy smoke that grounded firefighting aircraft early Saturday cleared enough to allow helicopters and a huge DC-10 tanker to start making drops in the afternoon.

Fire managers and more than 700 firefighters braced for another dose of hot temperatures and afternoon wind gusts up to 30 mph that could move flames closer to homes. Hundreds more firefighters were expected to arrive Saturday.

"This fire is consuming everything," fire spokeswoman Madonna Lengerich said. "The fire is so hot, it's just cremating even the biggest trees."

Ketchum, with a population of 2,700, and Sun Valley, with 1,400 people, were under "pre-evacuation orders," with authorities telling residents to be ready to leave if necessary.

The area's retail and dining districts normally are buzzing this time of year with tourists and summer residents. But the tight valley that bookends the communities was shrouded in thick smoke, keeping people indoors.

Some restaurants didn't open for Saturday breakfast and lunch. But as the haze lifted in the afternoon, activity picked up in Hailey and businesses started to reopen.

In addition to the government firefighters, some private insurers have sent in their own crews to provide structural protection for homes with values that can stretch into the millions of dollars, Blaine County Sheriff spokeswoman Bronwyn Nickel said.

"There are private engines that insurance companies have sent in," she said. "They're on site. They're working with our local firefighters and law enforcement."

In Utah, fire managers eyed the weather Saturday as crews continued battling several blazes, including the Patch Springs Fire in Tooele County.

The fire was relatively tame until Friday, when shifting winds pushed it over state Highway 199. Flames raced through Willow Springs, about 60 miles southwest of Salt Lake City, and forced the sudden evacuation of homes there and in the community of Terra, as well as a campground.

The highway and campground remained closed Saturday, but residential evacuations were being lifted.

Near Park City, Utah, crews reported progress battling a fire that destroyed eight homes earlier in the week.

That blaze has burned about 3 square miles and was 58 percent contained Saturday, spokeswoman Julie Booth said.