Story highlights MH370 disappeared March 8, 2014, on a flight from Kuala Lumpur, Malaysia, to Beijing

A part from an airplane wing was found July 29 on an Indian Ocean island

(CNN) Experts in France have not been able to determine with certainty whether a piece of airplane wing found July 29 on an Indian Ocean island belongs to MH370, the Malaysian airliner carrying 239 people that disappeared 2014, a French source close to the investigation told CNN on Saturday.

Judicial investigators know the part comes from a Boeing 777, but they say they still need to identify a number inside the wing part, called a flaperon, the source said.

When the flaperon washed up on Reunion island, a French territory, its discovery was considered possibly the first physical evidence that might help shed light on one of the world's greatest aviation mysteries.

Authorities have not been able to explain why the jet veered dramatically off course during a scheduled flight from Kuala Lumpur to Beijing on March 8, 2014, or to say where exactly its errant journey ended.

Though French authorities have not yet confirmed it, Malaysian Prime Minister Najib Razak said earlier this month the flaperon does, in fact, come from MH370.

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