Contact was lost with the OceanGate Expeditions craft – understood to be its Titan submersible – around an hour and 45 minutes into its dive on Sunday afternoon (18 June), according to the US Coastguard.

OceanGate’s expeditions take paying guests nearly 4,000 metres deep beneath the northern Atlantic to survey the wreckage of the famous ocean liner, which sank around 400 miles off the coast of Newfoundland, Canada, in 1912 on its maiden voyage to the US from Southampton.

Rescue operations are ongoing, with the assistance of US and Canadian government agencies and navies, as well as other deep sea firms. A US Coastguard press conference heard that as of Monday afternoon, the crew would have had approximately four days of oxygen left.

British billionaire business executive and explorer Hamish Harding, 58, chair of aircraft firm Action Aviation, is among those trapped on the craft, his family confirmed on Monday (19 June).

In a statement, OceanGate said: "We are exploring and mobilising all options to bring the crew back safely. Our entire focus is on the crew members in the submersible, and their families.

"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. We are working towards the safe return of the crew members."

OceanGate’s eight-day Titanic voyages start in St John’s, Newfoundland, and lead in from $250,000, approximately £200,000.