The "30 Mile Fire" is burning north of Winthrop in the Methow Valley. It started Monday between Andrews Creek and Sheep Creek, which both feed into the Chewack River, then exploded Tuesday afternoon, rapidly growing from 100 acres to more than 4,000.

U.S. Forest Service spokeswoman Debbie Kelly confirmed the deaths late Tuesday night. Kelly said the four had been missing since an explosive burst of flames - known as a "blow over" - overran a group of firefighters Tuesday evening.

All firefighters are equipped with emergency fire shelters. It is unknown of those killed had time to deploy them.

The identities and hometowns of the dead firefighters were not immediately released.

Several other firefighters were injured fighting the blaze, including one man who was airlifted to Harborview Medical Center in Seattle, in critical condition with burns over 30% of his body. He was later upgraded to serious condition.

No homes were being threatened in the remote area near the Paseyten Wilderness.

Steep Terrain

Elsewhere, steep, rocky canyons with virtually no escape route made it difficult to fight a 1,200-acre forest blaze burning north of Twisp in the North Cascades.

The third fire, burning about 80 miles to the southeast near Grand Coulee Dam, blackened some 200 acres of sage and grass.

No houses were immediately threatened in the Twisp area fire, but about 50 houses are located in the area. Thirteen families voluntarily evacuated the Libby Creek area Monday, said Art Tasker, a spokesman for the state Department of Natural Resources.

The fire was burning near the town of Carlton, about 10 miles south of Twisp in Okanogan County.

Worker Abandons Truck

A department worker trapped by the fire soon after it started Monday was forced to abandon his truck inside the fire line and walk out. He wasn't hurt, but it wasn't immediately known if the truck was burned, said Jim Archambeault, a spokesman for the U.S. Forest Service.

At least 400 firefighters were at the scene Tuesday. Planes flew over the fire to try to find the safest places to attack the blaze while keeping firefighters from getting stuck in a box canyon or draw with no way out, Tasker said.

The fire picked up intensity Tuesday afternoon as temperatures increased and fuels dried out.

'We Have Chances'

"What we're worried about, of course, is wind. Without the wind, we have chances. If the wind comes along we have to step aside for a while," Tasker said.

Crews had 20 wildland fire engines and 20 conventional fire engines. Four air tankers and three or four helicopters were dropping water and retardant on the flames.

The fire was reported at about 2:20 p.m. Monday and grew from 35 acres to 150 acres in about 45 minutes. It had grown to 400 acres by 8:30 p.m. and 1,000 acres at 11 p.m.

'Suspicious Origin'

The cause of the blaze was under investigation, Archambeault said. No lightning strikes were reported in the area.

"It was a little bit of a suspicious origin," he said.

Volunteer firefighters early on the scene reported hearing an explosion, Archambeault said.

"I'm not sure if it was the trees exploding, or something in the trees," said Twisp Fire Chief Dwain Hutson.

The department said the fire was burning on state, federal and private land. It was declared a project fire, meaning local authorities called for backup outside the region, and a fire management team was called in to coordinate. The team is based at Liberty Bell High School, between Twisp and Winthrop.

Communications Towers Threatened

The Coulee Dam fire, reported about 2 p.m. Tuesday, burned on a hill northeast of the town.

"The crews are trying to get a handle on it. If we can kick it where it's at, it will be OK," said David Nee, a spokesman for the U.S. Bureau of Indian Affairs.

No injuries were reported and no buildings were threatened, but the fire was headed in the direction the several communications towers, he said.

Crews from the BIA, Elmer City, Coulee Dam and the Bureau of Reclamation were fighting the blaze.