Rescuers in a remote area of the Atlantic Ocean raced against time early Tuesday to find a missing submersible carrying five people on a mission to document the wreckage of the Titanic.

The carbon-fibre submersible named the Titan, part of a mission by OceanGate Expeditions, carried a pilot, a renowned British adventurer, two members of an iconic Pakistani business family and a Titanic expert. Authorities reported the vessel overdue Sunday night about 435 miles (700 kilometres) south of St John’s, Newfoundland, according to Canada’s Joint Rescue Coordination Center.

Every passing minute, however, puts the Titan’s crew at greater risk. The submersible had a 96-hour oxygen supply when it put to sea at roughly 6 am Sunday, according to David Concannon, an adviser to OceanGate.

“It is a remote area — and it is a challenge to conduct a search in that remote area,” said Rear Admiral John Mauger, a commander for the US Coast Guard, which also is searching for the Titan.

Mauger told NBC’s “Today” show on Tuesday that his crews were working to prioritise underwater search efforts and get equipment there that can be helpful to the search.

“We’re working very, very hard to make sure that we bring all assets … to bring leading technical experts to understand what capability is available, what capability we can get to the team,” he said.

The Canadian research icebreaker Polar Prince, which was supporting the Titan, reportedly lost contact with the vessel about an hour and 45 minutes after it submerged. The Polar Prince was to continue to do surface searches throughout the night and a Canadian Boeing P-8 Poseidon reconnaissance aircraft will resume their surface and subsurface search in the morning, the US Coast Guard said on Twitter. Two US Lockheed C-130 Hercules aircraft also have conducted overflights.

The Canadian military also dropped sonar buoys to listen for any possible sounds from the Titan.

Ship-tracking satellite data from MarineTraffic.com analysed by The Associated Press showed the Polar Prince some 430 miles (690 kilometres) southeast of St John’s on Tuesday morning. The Bahamas-flagged cable layer Deep Energy was nearby as well, likely assisting in the surface search.

In an earlier email to the AP, Concannon said he was supposed to be on the dive but could not go. He said officials were working to get a remotely operated vehicle that can reach a depth of 3.7 miles (6 kilometres) to the site as soon as possible.

OceanGate’s expeditions to the Titanic wreck site include archaeologists and marine biologists. The company also brings people who pay to come along, known as “mission specialists.” They take turns operating sonar equipment and performing other tasks in the five-person submersible.

The Coast Guard said Monday that there was one pilot and four “mission specialists” aboard. However, OceanGate’s website suggests that the fifth person aboard may be a so-called “content expert” who guides the paying customers.

OceanGate said its focus was on those aboard 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 reestablish contact with the submersible,” it said in a statement.

Authorities have yet to formally identify those on board, though some names have been confirmed.

British businessman Hamish Harding, who lives in Dubai in the United Arab Emirates, was one of the mission specialists, according to Action Aviation, a company for which Harding serves as chairman. The company’s managing director, Mark Butler, told the AP that the crew set out on Friday.