(NewsNation) — With only a few days worth of oxygen on a submarine that went missing in the Atlantic Ocean, rescuers are racing against the clock.

A search is currently underway for the submarine, which was carrying a group of people to tour the ship wreckage from the Titanic. According to The Joint Rescue Coordination Centre in Halifax, Nova Scotia, the vessel was reported overdue around 9:13 p.m. Sunday, about 435 miles south of St. John’s, Newfoundland.

Called the Titan, there are five people on board the submersible, which brings Tourists to view the Titanic’s remains at about 12,000 feet at the bottom of the ocean.

With this kind of venture, Tim Taylor, founder of Tiburon Subsea, said there’s always the overhanging threat of losing assets, equipment and even whole submarines.

“It is very akin to climbing Everest for these people,” he said.

David Concannon, an adviser to the company Oceangate that owns the submarine, told the Associated Press the vessel had a 96-hour oxygen supply left.

Taylor said his understanding is that those on the submarine have about four days of life support on board.

“The clock is ticking as of now,” he said, during “NewsNation Now” on Monday.