A wildfire burning in northern Idaho (search) prompted the evacuation of about 100 homes, while power was severed to two communities, authorities said.

Additional residents have been warned to be prepared to evacuate but so far no structures have been lost to the fire burning southeast of Grangeville (search), said Robin Murray with the Idaho Department of Lands.

"We've estimated there are 70 residences ahead of the fire," Brian Shiplett, fire manager for the Idaho Department of Lands (search) in Coeur d'Alene, said Thursday.

The 2,000-acre fire crossed the South Fork of the Clearwater River Wednesday night and took out a power line, leaving residents in the towns of Elk City and Dixie without power, Murray said.

State Highway 14, the main road to the towns, remained open, but travelers were warned to drive at their own risk, authorities said.

Wildfires burning across the state have scorched almost 10,000 acres.

In Washington state, Gov. Christine Gregoire declared a wildfire emergency Thursday as firefighters scrambled to keep up with new lightning-sparked fires while battling a half-dozen other blazes burning in the eastern part of the state.

Officials were most concerned about a 1,500-acre blaze west of Spokane threatening 50 homes, 20 of which were evacuated, said Trooper Greg Pressel of the Washington State Patrol.

A 42,000-acre fire in the southeastern part of the state was 40 percent contained, but was burning south toward cabins in the Umatilla National Forest, said John Townsley of the Northwest Interagency Coordination Center in Portland, Ore.

Gregoire ordered state agencies to contribute to firefighting efforts, and announced she has alerted the National Guard for possible call-up if crews need help.

"We're facing a siege of wildfires across our state," she said Thursday. "There is a significant potential for us to continue to have large fires erupting on both sides of the state."

In Montana, the state's most troublesome wildfire joined another fire west of Missoula Thursday after firefighters intentionally torched unburned areas separating the two, officials said.

The fire, pushed by gusting winds in 90-degree weather, doubled in size Wednesday night, forcing firefighters to retreat and burning over three firefighters who deployed their fire shelters. They were not injured.

The National Interagency Fire Center said 33 large fires, totaling 222,510 acres, were burning Thursday, mostly in Western states. So far this year, wildfires have charred 5.5 million acres nationwide, compared with 5.6 million acres at the same time last year.