Authorities carry a large piece of plane debris that was found on Reunion island in the Indian Ocean, July 29, 2015. Investigators began working to determine if the wing part was from Malaysia Airlines Flight 370, which disappeared in March 2014. Reuters

Authorities became increasingly confident that debris found on Reunion Island on Wednesday belonged to the missing Malaysia Airlines Flight 370. If their suspicions are correct, the evidence could mean the plane did not nose-dive, but instead spiraled to a crash landing, they said.

The item found washed up on the beach of the Indian Ocean island was most likely a flaperon, part of a wing for a Boeing 777 jet, and was relatively intact, officials said.

The Malaysia Airlines flight was traveling from Kuala Lumpur, Malaysia, to Beijing in March 2014 when it vanished with a total of 239 passengers and crew members aboard. Wednesday's wreckage was found about 2,600 miles from what had been the search area, the Associated Press reported. The discovered wing piece measured about 6 feet long and was numbered -- but the number reportedly was not a serial or registration number.

Sources close to the Boeing 777 program told the Daily Beast on Thursday that the find bolsters a theory that the plane sped until it ran out of fuel. “It looks like the jet went into the water in a gliding/ditching attitude, because otherwise this wing component would have likely been completely destroyed,” the source said.

The Daily Beast reported that this theory was consistent with the "zombie flight" scenario that Boeing engineers recreated digitally. Computer-generated analysis shows the plane would have flown at its cruise height and speed for six hours until eventually running out of fuel. Flight 370 most likely did not nose-dive but "began a spiraling descent without power to the water and splashed down," the Daily Beast report said.

The wreckage has been shipped to Toulouse, France, where investigators will take a closer look. Experts from the French transportation department Bureau d’Enquetes et d’Analyses will lead the investigation.

Search crews have been dispatched to search the seabed area surrounding Reunion Island. Martin Dolan, who heads the Australian Transport Safety Bureau, told the BBC that there "is no other recorded case of a flaperon being lost from a Boeing 777."

Dolan said he is "increasingly confident" that the part belongs to Malaysian Airlines Flight 370, and that search crews will be able to locate the aircraft if that is the case.

"We are confident we have the quality of the search to cover that area and find the missing aircraft," he said.