San Francisco - About 70 searchers combed the area around the crash site of adventurer Steve Fossett's plane Friday as scientists were due to test a small piece of bone found near the plane.

The small bone, said by police to be about 5 centimetres by 3 centimetres was the only sign of possible human remains at the remote site. But it was far from clear that it was even human.

"When you find a bone fragment, there's no way to know until you give it to a forensic lab, whether it's human or animal," said Erica Stuart, a spokeswoman for the Madera County Sheriff's Department, which is handling the recovery. "We won't know until it's analyzed."

The searchers are in a race against an early winter storm, which could limit access to the area and possibly bury it in snow. Search teams on Thursday matched the wreckage with the plane that Fossett took off in before disappearing over the Sierra Nevada mountains last September.

Investigators said that the pattern of the wreckage made it almost certain that the crash was fatal. Debris from the wreckage was scattered across the mountainside, prompting National Transportation Safety Board acting chairman Mark Rosenker to call it "indicative of a high-impact crash, which appears to be consistent with a non- survivable accident."

In a statement, Fossett's widow Peggy thanked the searchers and the hiker who found his belongings.

"The uncertainty surrounding my husband's death over this past year has created a very difficult situation for me," she said. "I hope now to be able to bring to closure a very painful chapter in my life."

Searchers discovered the wreckage late Wednesday evening in a rugged wooded area in the Sierra Nevada Mountains after fanning out in a 15-kilometre radius from where hikers discovered ID cards, clothes and some 1,000 dollars in cash that appeared to belong to Fossett.

The items were found by ski shop owner Preston Morrow near the remote recreation town of Mammoth Lakes, close to the California- Nevada border and about 500 kilometres north of Los Angeles. He handed them over to the police after an approach to the Fossett family was rebuffed.

The new information was enough to reconvene a search that was halted over six months ago when air and ground searches failed to discover any trace of Fossett, 63, or the light plane that he was flying when he disappeared in September 2007.

Fossett vanished as he was apparently trying to find a site to attempt an assault on the world land speed record.

A billionaire financial trader, he set 116 records in sailboats, powered aircraft, balloons, airships and gliders.

He also swam the English Channel, drove in the 24 Hours of Le Mans car race, competed in Hawaii's Ironman Triathlon, sailed solo across both the Atlantic and Pacific oceans, climbed Argentina's 23,000-foot Aconcagua peak and competed in Alaska's Iditarod Trail sled dog race. (dpa)