Kuala Lumpur, Aug. 5 (Reuters): Malaysia confirmed early today that a piece of a wing washed up on an Indian Ocean island beach last week was from the Malaysian Airlines jet MH370, the first trace of the plane found since it vanished last year with 239 people on board.

"Today, 515 days since the plane disappeared, it is with a heavy heart that I must tell you that an international team of experts have conclusively confirmed that the aircraft debris found on Reunion Island is indeed from MH370," Prime Minister Najib Razak said in an early morning televised statement.

The announcement, by providing clear evidence that the plane crashed in the ocean, closes one chapter in one of the biggest mysteries in aviation history, but still leaves unanswered questions about precisely why it disappeared.

"Malaysia Airlines would like to sincerely convey our deepest sorrow to the families and friends of the passengers onboard Flight MH370 on the news that the flaperon found on Reunion Island on 29 July was indeed from Flight MH370," the airline said in a statement issued as soon as the Prime Minister had spoken.

"This is indeed a major breakthrough for us in resolving the disappearance of MH370. We expect and hope that there would be more objects to be found which would be able to help resolve this mystery," it said.

The airline's priority would be to update families and cooperate with authorities "on the investigation and recovery of this tragic accident", it added.

International crash experts had been examining the wing part found on France's Indian Ocean island of Reunion last week.

A statement from a French prosecutor involved in the case said there would be a news conference "on the subject of the disappearance of the Boeing MH370" in Paris.

The examination of the part is being carried out under the direction of a judge at an aeronautical test facility run by the French military at Balma, a suburb of the southwestern city of Toulouse, and witnessed by Malaysian officials.

Officials from the US and manufacturer Boeing were also on hand to advise whether the piece can be tied to Flight MH370, which went missing on March 8 last year while en route from Kuala Lumpur to Beijing. Boeing declined to comment. The airliner is believed to have crashed in the southern Indian Ocean, about 3,700km from Reunion.