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 RMS Titanic, the iconic ocean liner that sank more than a century ago.

The 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 another passenger. 

Authorities reported the vessel overdue Sunday night 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.

“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 U.S. Coast Guard, which also is searching for the Titan. 

“But we are deploying all available assets to make sure we can locate the craft and rescue the people on board.”

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 slated to do surface searches throughout the night and 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 American Lockheed C-130 Hercules aircraft also have conducted overflights.

In an email to the Associated Press, Mr. 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 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.