Portland, Ore. ? A fire engine fighting wildfires in the Klamath National Forest tumbled 800 feet off a steep, dirt road into a ravine Sunday, killing three firefighters, officials said.

Two others survived the plunge and were airlifted to the Mercy Medical Center in Redding, Calif., said Brian Harris, a the U.S. Forest Service spokesman. Their conditions were not known.

The five firefighters were returning about 2 a.m. from a 620-acre fire near the extreme northern California town of Happy Camp when the truck rolled off the ravine, Harris said. “Indications are they rolled in the worst possible place. It’s safe to say they rolled the entire 800 feet,” over rocky and partially wooded terrain, he said.

About 400 firefighters working the fires retreated Sunday and let the blaze burn unchecked, Harris said. No homes were threatened. The deaths brought to 12 the number of firefighters killed while fighting blazes in the West this summer.

Meanwhile, a wildfire near the Columbia River port town of The Dalles had grown to 12,000 acres Sunday and burned to within inches of some rural buildings.

Crews had the fire about 55 percent contained but gusty wind periodically kicked up the flames.

The blaze grew by 3,000 acres during the night, officials said.

Fire managers said Sunday they hoped to stop the fire from creeping down a hillside toward The Dalles. However, the town was not considered threatened.

In California’s Sierra Nevada, a blaze in and around Giant Sequoia National Monument had grown to 66,000 acres Sunday, after burning an additional 1,600 acres during the night.

The ancient sequoia trees weren’t completely safe but firefighters had minimized the threat, said fire information officer Jill Slater.

“They’re really getting a handle on it,” she said.

The wildfire was 30 percent contained.

Thirty-one major fires still active on Sunday around the West and in Alaska had burned about 491,000 acres, the National Interagency Fire Center reported.