A pink ribbon around a dead tree on a rocky ridge overlooking Crater Lake marks the last spot 8-year-old Sammy Boehlke's father saw him before the boy disappeared into the woods.

After five days of searching through rain, snow and subfreezing temperatures by some 145 trained personnel, that ribbon and a nearby spot where a tracking dog picked up his scent are the only signs of the boy since he ran away Saturday afternoon from his father's car while parked along the road circling the lake formed in a collapsed volcano at the crest of the Cascade Range.

"The only thing we've seen out there is animal tracks so far," said Chrissy Campanelli of Maple Falls, Wash., a member of the Rogue River Hotshots firefighting crew.

Pete Reinhardt, who oversees law enforcement at the park and is a division supervisor on the search, said they have not given up hope.

"The thing that's going to help this kid is if he had enough intuition, survival skills or just drive that he got into a rocky area where he could protect himself from the weather," said Reinhardt. "We haven't given up hope, because there are documented cases of people living a long time."

On Thursday morning, a party of more than 200 searchers planned an intense search of about 3,000 acres around the tree with its pink ribbon, said Mac Brock, natural resources officer for the park.

"They'll be walking along in one, long line," he said.

He said that searchers on Wednesday found a couple of lava tubes, and cave specialists would examine them Thursday to see if the boy had taken shelter there.

Sammy and his father, Kenneth Boehlke of Portland, were spending last weekend with family members at nearby Diamond Lake Resort, when the two of them decided to go up to Crater Lake for a hike.

They were driving along Rim Drive near the Cleetwood Cove trailhead when they pulled over at a turnout overlooking the nation's deepest and clearest lake, and got out of the car, said public information officer Rudy Evenson.

"The dad says it's time to go," said Evenson. "The boy decides he doesn't want to go, and decides to play hide and seek."

The boy, described by his family as exhibiting symptoms of autism, ran across the road and climbed a steep and rocky slope, disappearing over the top. His father looked for him, and after a couple hours flagged down a passing car, which relayed a call to 911.

The boy's parents have since stayed in seclusion at the park.

Park personnel mounted a search, but had just a short time before dark, and quickly realized that it was going to take a larger effort, said Mac Brock, park natural resources officer. They called in a National Park Service incident management team and search teams from Rainier to Yosemite national parks, nearby national forests, and local counties.

The search was concentrated first on the immediate area around the spot the boy was last seen, and has gradually moved out to cover a three-mile radius, Reinhardt said. About 145 people took part Wednesday.

"To have an 8-year-old boy out there with just slip-on shoes would be life and death on a summer night at this altitude," said Lindsay Clunes of the Corvallis Mountain Rescue Unit. "But late fall and turning to snow? Hopefully, he's hidden. But that just makes it tougher."

The 20 members of the Rogue River Hotshots spread out in a line, about 30 feet apart, and walked their assigned grid, looking under rocks, downed logs and trees in snow about 6 inches deep. A special rock-climbing rescue crew from Yosemite National Park has rappelled down the steep caldera wall. Boats have plied the shore of the lake. Horseback teams looked along an old road. A helicopter searched open areas. Each team logged in their search areas on Global Positioning System instruments, which were marked on a map at search headquarters.

On Tuesday, a tracking dog showed signs of recognizing the boy's scent, but other dogs failed to confirm it. The helicopter crew spotted tracks Wednesday going up a snow-covered knoll, but when they landed for a closer look realized they were left by wildlife. A search crew from the Fremont-Winema National Forest found a deflated yellow balloon on a downed log.

But nothing led them any closer to the boy.

"We were working high probability areas today, and just didn't see anything," said Jerry Heilman of the Corvallis Mountain Rescue Unit. "It would be nice to see something."

Chances the boy could have been abducted are considered slim, Reinhardt said. Traffic in the park is light in fall. The father only saw two cars go by in the time he searched. The two entrances to the park were staffed, and no one saw the boy in the cars leaving.

"We all want to bring an end to this to have some closure for the family," said Larry Kazakoff of Shady Cove, a member of the Rogue River Hotshots. "Some of us have nephews or nieces that age, a couple of us have children that age, so it's pretty tough."