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The "chest" is said to belong to a shipwreck and investigators initially thought they had finally found the plane, which went missing in 2014.

The mysterious object is nearly four kilometres beneath the surface of the southern Indian Ocean, and is sitting in a debris field known as Shipwreck #1 - thought to be the remains of a wooden cargo ship that sank in the early 19th century.

And the submerged vessel is near the wreck of a Peruvian transport ship named SV Inca, known as Shipwreck #2, which disappeared on its way to Sydney in 1911.

Both wrecks are situated south of the current search area for MH370, more than 2,000km off the coast of Western Australia.