Two pieces of "metallic debris" have been found on Reunion island, where a Boeing 777 wing part believed to belong to missing flight MH370 washed up last week, a source close to the investigation says.

Investigators on the Indian Ocean island took the debris into evidence as part of their probe into the fate of Malaysia Airlines flight MH370, however nothing indicated the piece of metal came from an airplane, the source said.

An AFP news agency photographer saw police collect one piece of debris, measuring about 100 square centimetres, on Sunday morning.

Police placed the debris — which had a sort of handle partially covered by leather and inscribed with two ideograms — in an iron case.

Also on Sunday, a man handed police a piece of debris measuring 70 centimetres found near the city of St Denis, guessing it was part of a plane door.

The discovery came after Malaysia confirmed that airplane debris found on the island on Wednesday had been officially identified as being from a Boeing 777, the same model as MH370 which vanished 16 months ago with 239 people aboard.

"We know the flaperon has been officially identified as being part of a Boeing 777 aircraft," transport minister Liow Tiong Lai said in a statement.

"This has been verified by French authorities together with aircraft manufacturer Boeing, US National Transportation Safety Board and the Malaysian team."

The barnacled 2-by-2.5-metre piece of wreckage was found by people cleaning up a beach on Wednesday.

Malaysia's transport ministry said it could take until this coming Wednesday before official confirmation the part is from flight MH370.

Reunion police leave a beach with metallic debris (being carried in a box). ( AFP: Richard Bouhet )

Identification of the debris may finally confirm the plane crashed into the sea after veering off course from its Kuala Lumpur to Beijing route, helping to end 16 months of lingering uncertainty for relatives.

Investigators believe someone deliberately switched off MH370's transponder before diverting it thousands of kilometres off-course.

Models of sea currents by oceanographers suggest it is plausible debris from the missing plane could wash up in the tropics.

A fragment of luggage that was also found in the area is with the aircraft debris in France for specialist DNA testing.

The debris will be analysed at a lab staffed by 600 experts that is operated by the French defence ministry.

If the serial number on the flaperon confirms it is from flight MH370, the laboratory can then use sophisticated tools to try to glean more information about the causes of the crash, such as whether its shape corresponds more to a mid-air explosion or a crash into the ocean.

ABC/wires