(NEWSnet/AP) — 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-fiber submersible, named Titan, part of a mission by OceanGate Expeditions, carried a pilot, a British adventurer, two members of an iconic Pakistani business family and a Titanic expert.

Authorities said the vessel overturned late Sunday about 435 miles 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 a.m. Sunday, according to David Concannon, an adviser to OceanGate. That means the oxygen supply could be depleted by  6 a.m. Thursday.

Canadian research icebreaker Polar Prince, which was supporting 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 U.S. Coast Guard said on Twitter. Two U.S. Lockheed C-130 Hercules aircraft also have conducted overflights.

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

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 the fifth person aboard may be a so-called “content expert” who guides paying customers.

OceanGate said its focus was on those aboard and their families.

Unlike submarines that leave and return to port under their own power, submersibles require a ship to launch and recover them. OceanGate hired Polar Prince to ferry dozens of people and the submersible craft to the North Atlantic wreck site. The submersible would make multiple dives in one expedition.

Experts said Monday that rescuers face steep challenges.

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