A ground team flown into the area by helicopter later confirmed the identity of the plane, a single-engine Bellanca Super Decathlon, which officials said seemed to have struck the mountainside head-on.
"It was a hard-impact crash, and he would've died instantly," said Jeff Page, emergency management co-ordinator for Lyon County, Nevada, who assisted in the search.
Most of the fuselage had disintegrated, with engine parts scattered over a debris field stretching about 150ft (46m) by 400ft (122m).
Search teams combing the site found more personal effects and what they described as a bone fragment, measuring 2 inches (5cm) by 1.5 inches (2.5cm).
SOME OF FOSSETT'S RECORDS
1998/2002: Long-distance for solo ballooning
2001/2002: Duration for solo ballooning
2002: First solo round-the-world balloon flight
First balloon crossings of Asia, Africa, Europe, South America, South Atlantic, South Pacific, Indian Oceans
Seven fastest speed sailing titles
13 World Sailing Speed Record Council titles
2001: Fastest transatlantic sailing
2004: Fastest round-the-world sailing
Round-the-world titles for medium airplanes
US transcontinental titles for non-military aircraft
"We found human remains, but there's very little," said Mark Rosenker, acting chairman of the National Transportation Safety Board. "Given the length of time the wreckage has been out there, it's not surprising there's not very much."
DNA tests would be performed on the material on a lab in California, he said.
Earlier, Madera County Sheriff John Anderson confirmed the find but injected a note of caution. "We don't know if it's human. It certainly could be," he said.
Officials now plan to remove the wreckage of the plane for reassembly and examination, and search for further human remains. But snow is expected over the weekend, which could potentially hamper the investigation.
Steve Fossett became the first person to circle the globe solo in a balloon in 2002 and had about 100 other world records to his name.
He vanished in September 2007 after taking off from a Nevada ranch for a solo flight.
For more than a year there was no trace of him, despite an intensive search.
But on Monday the hiker found identification documents belonging to him in undergrowth about 0.25 miles (0.4km) from the crash site, triggering an aerial search of a new area.
"The uncertainty surrounding my husband's death over this past year has created a very difficult situation for me," Mr Fossett's widow, Peggy, said in a statement. "I hope now to be able to bring to closure a very painful chapter in my life.
"I prefer to think about Steve's life rather than his death and celebrate his many extraordinary accomplishments."
British entrepreneur Sir Richard Branson also paid tribute to his friend and fellow adventurer.
"He led an extraordinary, absolutely remarkable life, and now we can remember him for what he was and move on," he said.
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