As transportation officials probed Tuesday's fatal crash of a firefighting helicopter, questions arose about why firefighters were in the area at all.

The crash occurred in the remote Trinity Alps Wilderness, between Green Mountain and Pony Mountain, at an elevation of about 6,000 feet. It killed nine people and injured four whose conditions ranged Thursday from good to critical.

The Buckhorn fire near Weaverville in Trinity County had burned about 18,700 acres as of Thursday afternoon. Much of the burn is on legally designated federal wilderness lands where no lives or structures are threatened.

But unlike some national forests, the Shasta-Trinity National Forest has no plan in place to allow fires to burn unchecked in some conditions.

This approach, dubbed "wildland fire use" by the Forest Service, has been embraced in many other forests and national parks. It can be a cheap and effective means to thin overgrown forests and restore more natural conditions.

Shasta-Trinity forest's policy "is all suppression," said forest spokesman Mike Odle. "We have made no progress implementing wildland fire use here."

Such a policy risks exposing firefighters to more dangerous situations.

"Eventually they're going to have to do serious fire planning," said Rich Fairbanks, a fire expert at the Wilderness Society, who spent 20 years as a Forest Service fire management official in Washington, Oregon and California. "Between global warming and urban sprawl, we've got to figure this stuff out ahead of time."

But Fairbanks was reluctant to criticize the decision to battle the Buckhorn fire.

"Without knowing, all we can say is it sucks, it really sucks," he said of the tragedy.

All of the dead and injured men lived in southern Oregon.

Three of the survivors remained at UC Davis Medical Center in Sacramento on Thursday. They are co-pilot Bill Coultas, 44, in critical condition; and Jonathan Frohreich, 18, and Michael Brown, 20, listed in good condition.

A fourth man, Richard Schroeder, 42, was in fair condition at Mercy Medical Center in Redding.

Missing and presumed dead are pilot Roark Schwanenberg, 54; Shawn Blazer, 30; Scott Charleson, 25; Edrik Gomez, 19; Matthew Hammer, 23; Bryan Rich, 29; and David Steele, 19. The identity of two others had not been released.

The dead remained at the remote crash site Thursday afternoon as investigators pieced together what happened.

Relatives and friends of the men described them as heroes.

Schroeder has worked as a firefighter for about two years, said his mother, Linda Parks. "We always worried that he might be in danger clear up there in the mountains," she said.

He told her about the accident in a brief phone call.

"The helicopter went up, and the propeller hit branches," she said. "The pilot said, 'Duck, we're going down.' "

Schroeder crawled through a broken window to safety. Parks said he suffered fractured vertebrae, scrapes and bruises.

"I am so sad for the families who lost someone," she said. "It could have been my son. We could have been planning a memorial service today."

Investigators released little information Thursday about what happened and would not confirm whether the helicopter struck anything.

"These brave individuals risk their lives to protect all of us," said Kitty Higgins, a board member of the National Transportation Safety Board, who is investigating the crash along with eight colleagues and other aviation officials. "Our job is to work to learn the lessons of this accident to make sure it doesn't happen again."

Among other things, investigators are looking for a voice data recorder that was aboard the helicopter.

"These are very difficult times," said Shasta-Trinity Forest Supervisor Sharon Heywood. She said counseling is available for firefighters and crew members. "Some of these people will carry this with them for the rest of their lives."

The helicopter that crashed was owned by Carson Helicopters Inc. of Pennsylvania, which has a regional office in Grants Pass, Ore.

Call The Bee's Matt Weiser, (916) 321-1264. Kim Minugh reported from Redding, and Cynthia Hubert reported from Sacramento. Bee researcher Sheila A. Kern also contributed to this report.