The missing adventurer's craft appeared to have crashed head-on into the mountainside.
Crews conducting an aerial search spotted what appeared to be wreckage in the Inyo National Forest near the town of Mammoth Lakes, Sheriff John Anderson said.
Ground crews confirmed it was Fossett's single-engine Bellanca plane.
Anderson said no human remains were found in the wreckage.
"It's quite often if you don't find remains within a few days. Because of animals, you'll find nothing at all," Anderson said.
Teams led by the sheriff's department were continuing the search for remains, while the National Transportation Safety Board was en route to probe the cause of the crash, he said.
Most of the fuselage disintegrated on impact, and the engine was found about 60m away, Anderson said.
Searchers began combing the rugged terrain after a hiker found identification documents belonging to Fossett earlier in the week. The wreckage was found less than 500m from where hiker Preston Morrow made his discovery.
The IDs provided the first possible clue about Fossett's whereabouts since he disappeared on September 3, 2007, after taking off from a Nevada ranch owned by hotel magnate Barron Hilton.
Aviators had previously flown over Mammoth Lakes, about 144 kilometers south of the ranch, in the search for Fossett, but it had not been considered a likely place to find the plane.
The most intense searching was concentrated north of the town, 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.
A judge declared Fossett legally dead in February following a search for the famed aviator that covered 51,800 square kilometers.
The California Civil Air Patrol and private planes from Hilton's ranch previously had flown over the area, but it was "extremely rough country," said Joe Sanford, undersheriff in Lyon County, Nevada, which was involved in the initial search.
Fossett made a fortune trading futures and options on Chicago markets. He gained worldwide fame for more than 100 attempts and successes in setting records in high-tech balloons, gliders, jets and boats.
In 2002, he became the first person to circle the world solo in a balloon. He was inducted into the National Aviation Hall of Fame in July 2007.
He also swam the English Channel, completed an Ironman Triathlon, competed in the Iditarod dog sled race and climbed some of the world's best-known peaks, including the Matterhorn in Switzerland and Mount Kilimanjaro in Tanzania.
