Relative of victims have met Australian officials to discuss progress made by the official search
Charred debris, possibly belonging to the missing MH370 plane, has been handed to investigators - raising the prospect of a flash fire on board the ill-fated jet.
An American amateur investigator handed over several pieces of blackened debris to Australia's Transport Safety Bureau on Monday in what may prove to be a breakthrough in one of the biggest mysteries in aviation history.
Blaine Gibson said the material, which had washed up in Madagascar, included what appeared to be an internal panel.
"The top layer of paint has been singed, scorched black," he told Australia's Channel 7 of one piece. "It also shows some signs of melting... as you see when something is exposed to fire.
"It appears to be from the interior of the plane but not the main cabin, perhaps the cargo hold, perhaps the avionics bay."
The Malaysia Airlines Boeing 777 vanished en route from Kuala Lumpur to Beijing on 8 March 2014 with 239 people on board.
The reason for the plane's disappearance remains a mystery and its final resting place has never been found.
Mr Gibson, a lawyer from Seattle, told the Australian Broadcasting Corporation the pieces may prove to be a "real game changer" if they were found to belong to MH370.
"One of the theories is that there was a fire on the plane," he said, noting that until now there has been no evidence to support this theory.
Australia's Transport Safety Bureau, which is co-ordinating the search for the plane, has said it is seeking advice from Malaysian authorities on how to proceed.
The debris was handed over as relatives of some of the victims met Australian officials to discuss progress made by the official search.
The eight family members called on the investigating nations - Australia, China and Malaysia - to do more to uncover evidence, expressing frustration that the search so far has turned up little credible information.
"It's very impressive that one private individual citizen, Blaine Allen Gibson has managed to find up to 15 pieces of aircraft debris and we hope that these three nations do more than just hope that by fluke people find more debris," said Grace Nathan, whose mother Anne Daisy was on the plane.
A search of a final 120,000sq km zone is due to be completed in December.
The area was defined under the "most likely" scenario that no one was at the controls as the plane ran out of fuel.
However, the latest hunt has failed to find a single piece of debris, raising suspicion that the crash site may be elsewhere.
The first piece of debris found from MH370 - a two-metre wing part known as a flaperon - washed up on the French Indian Ocean island of Reunion in July 2015.