They were building a line around the 8,200-acre fire in the Okanogan National Forest, using trails and roads and natural firebreaks.
Meanwhile, the bodies of the four killed firefighters were undergoing autopsies in Wenatchee. Chelan County Coroner Dr. Gina Fino expects to have results Friday at the earliest.
The dead are 30-year-old Tom Craven of Ellensburg; 18-year-old Karen Fitzpatrick of Yakima; 21-year-old Devin Weaver of Yakima; and 19-year-old Jessica Johnson of Yakima.
A firefighter who was burned in a burnover remained in serious condition at Harborview Medical Center in Seattle. The hospital says the 21-year-old Yakima man is scheduled for skin graft surgery on Monday because of deep burns on his hands. He's expected to remain in the hospital for six to eight weeks.
A Forest Service investigation team was interviewing firefighters who survived the burnover. The team also was looking at the scene where they were trapped.
Deputy Forest Service Chief Jim Furnish says the agency is grieving the loss of the firefighters and doesn't want it to happen again.
Also on Thursday, fire and county officials said they have contacted or verfiied locations of all known hikers and campers in the vicinity of the fire. No one was in danger.
'A Dire Situation'
More than 40 firefighters have died in 15 entrapments on fires since 1990.
Investigators are trying to determine why emergency tent shelters failed to save the lives of the four firefighters caught in the forest fire near Winthrop. The small one-person tents carried by firefighters are a last resort.
"All of the firefighters were in a dire situation," said forest supervisor Sonny J. O'Neal. "The fire blew up as firefighters were trying to evacuate ... all of them were in serious threat of losing their lives."
Two Lives Saved
As the flames roared toward them from a steep, rocky draw, the firefighters scrambled for their trucks. Those who couldn't make it grabbed their emergency shelters, aluminum-and-fiberglass tents designed to shield them from the heat and flames. One firefighter pulled two civilian campers into her one-person shelter, likely saving their lives.
Jason Emhoff's four crewmates were partway down a wooded ravine when the flames roared up. They made a dash for the Chewuch River, at the bottom of the ravine, but the fire was moving too fast. They had just shaken out their shelters and were crawling inside when the fire overtook them.
All four died in the blast of heat and flames Tuesday, the worst loss of life since 14 firefighters were killed near Glenwood Springs, Colo., on July 6, 1994.
The Forest Service on Wednesday pulled the remaining crews back from the fire.
"I would think they'll be extra cautious in putting anybody out on this fire," Forest Service spokesman Jim Archambeault said.
'A Bad Fire Year'
The woods in north-central Washington have been parched by the area's worst drought since 1977.
"Everybody knew this was going to be a bad fire year, with the lack of moisture this winter and several dry summers," Archambeault said.
On Tuesday, the ground was dry but the weather was calm when the 21 firefighters were sent in to snuff out hot spots from the small blaze, believed to have been sparked by an unattended campfire.
When the wind came up, the fire blew to 2,500 acres in just over two hours.
"What we had was a very calm situation that suddenly became very volatile," Forest Service spokesman Rick Acosta said. "There were high winds, very high temperatures of 100 degrees and low humidity. That makes for very tough fire behavior, and that's what we got."
Missing Gloves May Have Saved Life
Emhoff was the only survivor of his five-person crew. His father, Steve Emhoff, believes his son's missing gloves may have saved him.
The 21-year-old had removed his work gloves earlier in the day. When the flames rushed in, the fire's heat was too intense for him to hold the emergency shelter. With the heat searing his hands, Emhoff ditched the tent and ran for the nearest truck.
"He knew what he was up against," his father said.
Emhoff was in serious but stable condition with burns over 25 percent of his body, including his face and torso. His hands had "full-thickness burns" that will require skin grafts if doctors can save them, said Harborview Burn Center director David Heimbach.
The firefighters' emergency fire shelters, which take about 45 seconds to deploy, have been standard issue for the Forest Service since 1970 and are credited with saving at least 250 lives. A redesign is under way based on tests showing that direct flames can break down the materials.
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