Examination of the debris is expected to shed more light on the cause of the catastrophic implosion that shattered the Titan on June 18.

The somber announcement ends a multinational search-and-rescue operation that captivated the world since the tiny tourist craft went missing in the North Atlantic four days ago.

Even if the submersible is located, retrieving it presents huge logistical challenges, given the extreme conditions thousands of metres below the surface.

The fate of the submersible and those aboard remains a mystery as search teams from the US, Canada and France mount an intensifying search in an area of open sea larger than the state of Connecticut.

The wreck of the Titanic, a British ocean liner that struck an iceberg and sank on its maiden voyage in April 1912, lies about 1,450km east of Cape Cod, Massachusetts, and 644km south of St John's, Newfoundland.

The vessel has a range of 96 hours for a crew of five, and might have had 70 or more hours of remaining oxygen as of Monday afternoon.