More than a year after adventurer Steve Fossett disappeared, search crews have found human remains scattered amid the wreckage of his plane in eastern California, investigators said Thursday.

The National Transportation Safety Board would not reveal what exactly was found, but they said the discovery was enough to provide the coroner's office with a DNA sample.

Earlier in the day, Madera County sheriff John Anderson said the single-engine aircraft Fossett was piloting likely crashed head-on into the mountainside in the Inyo National Forest near the town of Mammoth Lakes.

Most of the fuselage disintegrated on impact, and the engine was found quite a distance away, Anderson said.

The discovery of the remains came after Anderson said searchers would walk arm-to-arm for about a kilometre-and-a-half around the crash site.

Search sparked by ID discovery

The search started on Wednesday in the rugged part of eastern California after a hiker found identification documents, some of which were confirmed by the Federal Aviation Administration and local police to match up with the American adventurer.

Preston Morrow was hiking just west of the town of Mammoth Lakes on Monday and said he found Fossett's FAA identity card, a pilot's licence, a third ID and $1,005 cash tangled in a bush off a trail.

Local police authenticated two of the documents, including Fossett's pilot's licence.

The IDs were the first sign of Fossett's whereabouts since he vanished after taking off in a borrowed plane from a Nevada ranch owned by hotel magnate Barron Hilton on Sept. 3, 2007.

After a search spanning 50,000 square kilometres, the famed aviator was declared legally dead by a judge in February.

Mammoth Lakes, about 145 kilometres south of the ranch Fossett took off from over a year ago, had not been considered a likely place to find the plane.

Aviators flew over the area but given what searchers knew about sightings of Fossett's plane, his plans for when he had intended to return and the amount of fuel he had in the plane, they concentrated their search north of the town.

Fossett made his fortune trading futures and options on Chicago markets but gained worldwide fame for his attempts and successes in setting records in high-tech balloons, gliders, jets and boats.

In 2002, he became the first person to circumnavigate the globe solo in a balloon and was inducted into the National Aviation Hall of Fame five years later.

Fossett also participated in many of the world's athletic competitions - he swam the English Channel, completed an Ironman Triathlon, competed in the Iditarod dog sled race and climbed some of the world's best-known mountains.

With files from The Associated Press