A fast-moving central Idaho wildfire forced the evacuation of 2,250 homes near the tourist towns of Hailey and Ketchum as firefighters lost ground on Saturday against the blaze that also threatens the Sun Valley ski resort.

Blaine County Sheriff Gene Ramsey called for occupants on the outskirts of both towns to leave without delay. He expanded evacuation zones to include residential developments north of Ketchum.

The fast-moving wildfire has burned more than 92,000 acres (37,230 hectares) of sagebrush flats, pine forests and granite canyons in the Sawtooth Range west of a highway that connects Hailey, a town of about 8,000 people, to Ketchum and Sun Valley to the north.

More than 1,000 people have fled upscale subdivisions on the southern outskirts of Ketchum, where some homes are worth tens of millions of dollars. The area features the vacation getaways of such celebrities as former California Governor Arnold Schwarzenegger and actor Tom Hanks.

The blaze has sent towering columns of smoke over the tourist towns nestled in a narrow mountain valley known for premier hiking, biking, fishing and skiing.

An animal shelter on the west side of Hailey, where flames enveloped a mountain ridge and raced toward a city park below, was safely emptied of dogs and cats, said Blaine County Deputy Sheriff Anita Selner.

Hundreds of firefighters were battling to keep flames from crossing to the east side of the highway that links the three towns and is the only developed road out of the valley.

The so-called Beaver Creek fire has claimed one primary residence, one bunkhouse and six other buildings since being sparked by lightning on August 7, federal fire information officer Sandy Miller said.

Roughly 30 people stayed overnight at an American Red Cross shelter in Hailey, where onlookers gathered as air tankers equipped with fire retardant and helicopters with water buckets flew overhead.

"A lot of people are just watching the fire and our customers are talking about nothing else," said Alexis Sualez, barista at Zaney's River Street Coffee House in Hailey. "People are pretty worried."

The valley is crisscrossed by recreation trails and gated subdivisions of log mansions and luxury homes that border the Sawtooth National Forest.

It is one of several high-end enclaves in Western states that have been menaced in recent days by wildfires fueled by record heat, drought and fierce winds.

Crews grappling with the Beaver Creek fire were warned that conditions could rapidly deteriorate amid rising temperatures and gusting winds.

"There is definitely a sense of anxiety," said Blaine County spokeswoman Bronwyn Nickel as residents and vacationers fled the area. - Reuters