A MAJOR search and rescue mission is underway after a tourist submarine has gone missing near the wreck of the Titanic.

A submersible vehicle that takes up to five tourists to view the wreckage of the Titanic has gone missing with an unclear number of people on board.

A British adventurer is among those aboard. Hamish Harding is a UK billionaire and chairman of private plane firm Action Aviation.

On social media this weekend, Harding said he was “proud to finally announce” that he would be aboard the mission to the wreck of the Titanic.

Lieutenant Commander Len Hickey said a Canadian Coast Guard vessel and military aircraft were assisting the search effort, led by the US Coast Guard in Boston.

The Boston Coastguard are co-ordinating the operation with the Joint Rescue Coordination Centre in Halifax, Nova Scotia. A Canadian military aircraft and a Canadian Coast Guard vessel are assisting the search effort.

This submersible, which pings back messages every 15 minutes to the mainland, has not been heard from for more than seven hours. This is creating considerable concern.

It is understood there are emergency provisions onboard such as oxygen, food and warm clothing which are supposed to last for 96 hours.

Both tourists and scientists use the vessels, owned by US private company OceanGate Expeditions, to take part in deep sea expeditions.

“We are deeply thankful for the extensive assistance we have received from several government agencies and deep sea companies in our efforts to re-establish contact with the submersible,” the company said in a statement.

A statement continued: "We are exploring and mobilising all options to bring the crew back safely. Our entire focus is on the crewmembers in the submersible and their families."

"We are working toward the safe return of the crewmembers." 

The wreck of the Titanic, which famously sank 101 years ago on its maiden voyage from Southampton to New York, lies about 3800m deep off the coast of Newfoundland, Canada in the North Atlantic Ocean.

Since the wreckage was discovered in 1985, it has been slowly succumbing to metal-eating bacteria, and some have predicted it could vanish in decades as holes grow in the hull and sections disintegrate.

In describing its first expedition, OceanGate said that in addition to archaeologists and marine biologists, the expeditions would also include roughly 40 paying tourists who would take turns operating sonar equipment and performing other tasks in the five-person submersible.

The initial group of tourists was funding the expedition by spending anywhere from 100,000 to 150,000 US dollars (£78,000 to £117,000) each.