A wing part washed up on an island in the western Indian Ocean may be the first trace of Malaysia Airlines Flight 370.

Malaysia's prime minister said the debris found on the French island of Reunion will be sent to Toulouse in France for investigation.

"We have had many false alarms before, but for the sake of the families who have lost loved ones, and suffered such heartbreaking uncertainty, I pray that we will find out the truth so that they may have closure and peace," Najib Razak said on his personal blog.

Mr Najib promised to make any new information public quickly.

Air safety investigators - one of them a Boeing investigator - have identified the component as a "flaperon" from the trailing edge of a Boeing 777 wing, a US official said. Flight 370, which disappeared March 8 2014, with 239 people on board, is the only 777 known to be missing.

"It's the first real evidence that there is a possibility that a part of the aircraft may have been found," said Australian transport minister Warren Truss, whose country is leading the search for the plane in a remote patch of ocean far off Australia's west coast.

"It's too early to make that judgement, but clearly we are treating this as a major lead," he added.

Flight 370 had been travelling from Kuala Lumpur to Beijing, but investigators believe based on satellite data that the plane turned south into the Indian Ocean after vanishing from radar. If the wing part is from the Malaysian plane, it would bolster that theory and put to rest others that it travelled north, or landed somewhere after being hijacked.

The wing piece is about 2 meters long. Investigators have found a number on the part, but it is not a serial or registration number. It could be a maintenance number, which may help investigators figure out what plane it belongs to.

Flaperons are located on the rear edge of both wings, about half way between the fuselage and the tips. When the plane is banking, the flaperon on one wing tilts up and the other tilts down, which makes the plane roll to the left or right as it turns.

The piece could help investigators figure out how the plane crashed.

A massive multinational search effort of the southern Indian Ocean, the China Sea and the Gulf of Thailand has turned up no trace of the plane.

The last primary radar contact with Flight 370 placed its position over the Andaman Sea about 230 miles north west of the Malaysian city of Penang. Reunion is about 3,500 miles south west of Penang, and about 2,600 miles west of the current search area.

Indian Ocean currents is likely to bring floating debris to the east coast of Africa, said aviation safety expert John Goglia, a former member of the US National Transportation Safety Board. But it is unlikely to provide much help in tracing the ocean currents back to the location of the main wreckage, he said.

"It's going to be hard to say with any certainty where the source of this was," Mr Goglia added. "It just confirms that the airplane is in the water and hasn't been hijacked to some remote place and is waiting to be used for some other purpose. We haven't lost any 777s anywhere else."

The prefecture of Reunion said the source of the debris has not been identified, nor has it been definitely found to be from a Boeing 777. Reunion authorities have asked France's aviation investigative agency, known as the BEA, to coordinate with international investigators, notably the Malaysian and Australian authorities.

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