YAKIMA, Wash. (AP) - Federal investigators on Wednesday picked through the debris of an airplane crash that killed 10 people in central Washington's rugged Cascades, hoping to determine what caused the plane to nosedive into dense timber.

A pilot and nine skydivers died in the crash Sunday evening as they were returning from a weekend skydiving trip near Boise, Idaho. Authorities have declined to speculate on what might have caused the plane to nosedive into the trees just east of the Cascade crest.

Investigators with the Federal Aviation Administration and the National Transportation Safety Board spent hours at the crash site Wednesday, and were expected to return Thursday, said Debra Eckrote, the NTSB's Northwest regional director.

They will try to document as much as they can from the wreckage, including readings from any intact control panels, the position and condition of airplane parts and any flight control documentation.

The debris field has been estimated at 60 feet by 100 feet.

"It's all going to depend on just how badly damaged the aircraft is," she said.

Once the site investigation has been completed, recovery of the aircraft will begin. Officials will continue their review in a controlled environment indoors after they remove the airplane from the mountain, she said.

"Usually, in an aircraft this size and the terrain, you're really limited in what you can do," Eckrote said.

The airplane crashed into thick timber at 4,300 feet, about 45 miles west of Yakima near the Goat Rocks Wilderness Area.

Eckrote said the aircraft was not required to be equipped with a flight data recorder, which on larger, commercial planes can tell what happened in the minutes before an accident.

A hunter in the crash area reported seeing the low-flying Cessna Caravan 208 on Sunday night. The aircraft appeared to be in trouble, with the engine whining loudly, followed by silence, authorities said.

The plane, a single-engine turboprop built in 1994, was reported missing early Monday. Searchers found it Monday evening after following the scent of fuel to the crash site, within 200 yards of its last radar ping.

The plane was registered to Kapowsin Air Sports of Shelton, located near Olympia.

Geoff Farrington, Kapowsin's co-owner, said the family-owned company had never before lost a plane. He also said the plane had never experienced mechanical problems.

The FAA had warned in recent years that pilots should avoid flying the Cessna Caravan 208 in many icy conditions after receiving reports that pilots had difficulty maintaining altitude and control of the aircraft during such conditions.

Mike Robertson, an FAA investigator at the scene, declined to speculate whether the weather might have played a role in the crash.

A cold front had just swept through the area near White Pass where the plane went down. The temperature at White Pass was 33 degrees at 5,800 feet, it was overcast with light precipitation and probably clouded over between about 4,500 feet and 5,800 feet between 7 p.m. and 8 p.m. Sunday, the National Weather Service said.

The skydivers were affiliated with Skydive Snohomish, a company that operates a training school and skydiving flights at Harvey Field in Snohomish County, about 20 miles north of Seattle.

Their bodies were transferred Wednesday from Yakima to Seattle, where King County officials will assist in the identification process.

---

The victims of a plane crash Sunday evening in Washington's central Cascades that killed the pilot and the nine skydivers on board:

- Ralph Abdo, 27, of Issaquah, Wash., was a program manager at Microsoft, where he worked for the past seven years, but he thrived on extreme sports.

"He would not do wind surfing casually like most people do," recalled his girlfriend, Diana Antczak. "He took it up and had to do freestyle moves and front loops, back loops."

His older brother, Nadim, said Abdo was not satisfied with the wind-surfing boards available on the market so he learned to work with fiberglass and started making his own.

He took up skydiving this past winter.

- Landon Atkin, 20, of Snohomish, Wash., took up skydiving last year, "did it once and got hooked," said Mitch Sieber, a friend since kindergarten.

He played drums in a pop-punk band, Rumor Has It, and loved to be on stage and was also known for his enthusiasm as a friend, Sieber said.

"Everyone loved Landon the minute they met him," Sieber said. "He was the most outgoing friend I had."

He was a graduate of Snohomish High School and was attending Cascadia Community College in Bothell. He worked as a parachute packer at Harvey Field in Snohomish. He aspired to be a skydiving instructor.

"He definitely lived life to the fullest and loved the skies," said Staci Boyd, another friend since kindergarten.

- Michelle Barker, 22, of Kirkland, Wash., announced just after her 18th birthday that she was going to go skydiving.

"We all went out and watched her do that, but we didn't know how much it was going to take over her life," said her stepfather, Rich Williams. "After that, she was either at work or the jump zone."

The Boise, Idaho, native moved to the Seattle area in April so she could get more skydiving experience. Williams guessed she had made about 50 jumps.

"If she got it in her mind that she was going to do something," Williams said. "There was no stopping her."

A graduate of Centennial High School in Boise, Barker was remembered by her high school counselor as a good student and an all-American girl.

"She was always, always the very adventurous type," Carol Joplin said. "She wanted to have as many adventures as she could."

- Casey Craig, 30, of Bothell, Wash., was a veteran of more than 600 jumps, introduced to the sport by his older brother, Kelly.

The last family photo of Craig and his siblings was taken two weeks ago at 13,000 feet. His sister, Ivy Green, said he wanted to make the most of the last nice day of the year.

"I want to make sure people know he didn't die skydiving - it was a plane crash," said his mother, Wanda Craig.

Ryan Shipley, a Lake Stevens, Wash., skydiver, said Craig was a social magnet, hosting "Wine Wednesdays" every week at his Bothell home. He had already mailed out invitations for a Halloween party, Shipley said.

Craig worked for the family business installing and cleaning carpet and upholstery.

- Cecil Elsner, 20, of Lake Stevens, loved skydiving so much that he even packed a parachute when he was skiing, his other passion.

At Whistler Blackcomb in British Columbia last winter, Elsner used his 'chute to fly - literally - off cliffs, said Mike Tracy, who helped run the Elsner family business, Mount Pilchuck Ski & Sport.

As a teen, he would sneak out during work breaks to take skydiving lessons. Once, he was blown off course during a dive and hours passed before he returned - embarrassed but glad to be alive.

On his MySpace Web page, the Western Washington University student described skydiving as an enlightening escape from a world of turmoil and traffic jams.

"You see the slightest curve of this massive globe looking off into the horizon and get some sense of your place in it all," he wrote.

- Bryan Jones, 34, of Redmond, Wash., was considered a human, quiet, even shy guy on the job for the past seven years at Microsoft, but after work he hopped on his motorcycle to head to Harvey Field to skydive.

"He was pretty dedicated," said Shawn Starr, a Skydive Snohomish instructor. "He would sit in traffic for hours just to make one jump at sunset."

He had made more than 1,000 jumps and helped lead the Seattle Skydivers club. He recently began "canopy piloting," a more specialized skydiving sport, said skydiver Dave Correia.

"He knew what he was doing and he did it well," said Ryan Shipley, another skydiver and friend.

- Phil Kibler, 46, of Troy, N.Y., and Snohomish, the pilot of the aircraft, was making his last flight of the season before heading home to the East Coast to be with family.

The 10-year veteran pilot had biked through Ireland, spent six weeks in Africa and traveled to Australia and rugged Baffin Island, on the Arctic edge of northern Canada.

Kibler had agreed to take the group of friends to a weekend skydiving event in Boise before traveling to New York on a cross-country fly fishing trip.

Before moving to Snohomish County, Kibler left a pharmaceutical job in Montreal for the chance to be a pilot, his brother said. He had a doctoral degree in microbiology and his scientific background led him to pilot whale researchers over the Atlantic Ocean.

The single man spent this past summer working for Skydive Snohomish, piloting flights from Harvey Field in Snohomish.

Bill Kibler said his older brother led a very lucky life.

"My brother was able to do what he absolutely loved doing," he said. "Not a lot of people get that opportunity."

- Hollie Rasberry, 24, of Bellingham, Wash., fell in love with skydiving after trying it a year ago, said Kristy Knopp, the owner of the restaurant where she worked. She also was pursuing a degree at Whatcom Community College.

"She picked up every extra shift she could just so she could go sky diving because it was so expensive," Knopp said.

Knopp said Rasberry became hooked on skydiving after trying it while on vacation in Las Vegas.

"Everything she did, she did it 100 percent. She was a really fun person; a very loving person," Knopp said.

- Jeff Ross, 28, of Snohomish, had only been skydiving for a year, but was already working at Skydive Snohomish, packing parachutes to supplement his income as a shift manager at a pharmacy. He wanted to be a skydiving instructor.

On windy days, he helped jumpers collapse their parachutes as they landed so they wouldn't be dragged across the ground.

"I definitely trusted him when he was out there," said skydiving instructor Shawn Starr. "I knew he'd be out there to catch me."

On his MySpace page, Ross lamented the shortage of pirates in the world.

- Andrew Smith, 20, of Lake Stevens, said his favorite superhero was Superman, because he could fly.

When he boarded the airplane with his friends Sunday afternoon, his girlfriend asked him not to go. Julianne Hezlep said he sent her a text message form the airplane.

"It said he will love me until the end of the world. I will keep that forever," she said.

He was working and training to become an engineer on a ferry between Seattle and Victoria, British Columbia.

During the weekend trip to Idaho, he visited Hezlep at Northwest Nazarene College in Nampa. She spend the weekend hanging out and enjoying a campfire with Smith and his skydiving friends.

"They died doing what they loved," she said. "The all had smiles on their faces. They were happy and we need to be happy that they were happy."