Two firefighters were overrun by flames and killed after rappelling to the ground to clear a helicopter landing zone in a national forest burning in central Idaho.

The Forest Service expressed their condolences to family and friends of Jeff Allen, 24, of Salmon, and Shane Heath, 22, of the Boise area. Allen became a seasonal firefighter in 1999. Heath, a Boise State University student, had been a wildland firefighter for four years.

"Both young men were Forest Service employees who died protecting the lives and property of their fellow Americans," Forest Service Chief Dale Bosworth said Wednesday.

All firefighters were pulled from the blaze in the Salmon-Challis National Forest and an investigation of the deaths was under way. It was unclear when the fight to contain the blaze would resume.

"Firefighter safety is the No. 1 priority," Forest Supervisor George Matejko said. "The stand-down ensures that those involved on the fire have an opportunity to deal with the impact of the tragedy."

The forest fire, about 130 miles south of Missoula, Mont., was caused by lightning and first reported Sunday night. Hot temperatures and wind blew it up from 120 acres to about 1,000 acres, officials said.

Allen and Heath were the eighth and ninth firefighters assigned to wildfires to die since February nationwide, said Alan Hoffmeister, a spokesman for the National Interagency Fire Center in Boise. Only one of the previous deaths was by fire, while the others were helicopter crashes and accidents.

"This fire behavior has been very unusual in the extreme. The conditions that we're seeing at this time of the year are unsurpassed and haven't been witnessed in recent memory," U.S. Forest Service spokeswoman Erin O'Connor.

"The dryness of the trees and other shrubs, the high temperatures of over 100 degrees for weeks, the relative humidity down to around 16 percent - all those factors contribute to very extreme fire behavior."

Another Idaho blaze grew to about 14,000 acres in the Boise National Forest and was about three miles away from the small town of Atlanta on Wednesday evening. One outbuilding was lost to the flames.

The National Interagency Fire Center said there were 49 large fires burning in the West, with 359,380 acres of active wildfires. Other states with large fires included Arizona, California, Colorado, Montana, New Mexico, Nevada, Oklahoma, Oregon, South Dakota, Utah, Washington and Wyoming.

In east-central Montana, a wildfire has burned about 122,000 acres near Brusett but was considered 40 percent contained late Wednesday. A new fire that grew to 4,000 acres in extreme southwestern Montana was expected to merge with another, which already has burned on more than 3,000 acres.

Officials in Washington state said Wednesday they probably will not be able to put out a huge wildfire near the Canadian border until heavy rain or snow help extinguish the flames later this year.

The 59,000-acre, lightning-caused fire in a north-central Washington wilderness area was generating winds so strong it has ripped trees out by their roots and thrown them ahead of the flames.