The search is ongoing for the missing submarine that brought people to see the Titanic

Rescue operations were under way deep in the waters of the Atlantic Ocean on Monday to search for the submarine that brought people to view the wreckage of the Titanic.

The Joint Rescue Coordination Center in Halifax, Nova Scotia said the vessel was reported past time at about 9:13 p.m. Sunday, about 435 miles south of St. John's, Newfoundland. Lt. Cmdr. Len Hickey said Canadian Coast Guard vessels and military aircraft are assisting the search effort, which is being led by the US Coast Guard in Boston.

OceanGate Expedition confirmed the search for the five-man submarine and said the focus was on those on board and their families.

“We are grateful for the extensive assistance we have received from several government agencies and deep-sea companies in our efforts to re-establish contact with submarines,” the company said in a statement. “We are working towards the safe return of the crew members.”

Chris Parry, a retired British naval admiral, told Sky News the rescue was “a very difficult operation.”

“”The nature of the seabed is actually very bumpy. The Titanic itself lies in a ditch. There is a lot of debris around. So trying to differentiate with sonar in particular and trying to target the areas that you want to search with other submarines is going to be very difficult.”

In 2021, OceanGate Expeditions embarked on what is expected to be an annual voyage to chronicle the damage to the iconic ocean liner that struck an iceberg and sank in 1912, killing all but about 700 of the approximately 2,200 passengers and crew. Since the discovery of the wreck in 1985, it has slowly died from metal-eating bacteria, and some estimate the ship could be gone in a matter of decades as a gaping hole in the hull and its shattered parts.

Early tourist groups funded expeditions spending anywhere from $100,000 to $150,000 each.

The 2023 OceanGate Expedition is the third to the site of a sunken ocean liner to document the damage and marine life.

The trip is scheduled to depart from St. John's, Newfoundland, in early May and finished in late June, according to court documents filed by the company in April with the US District Court in Virginia handling the Titanic matter.

OceanGate chartered the Canadian ship Polar Prince, a medium-duty icebreaker formerly operated by the Canadian Coast Guard, to transport dozens of men and submarines to the North Atlantic wreck site.

The five-person submarine, named Titan, is capable of diving 4,000 meters or 13,120 feet “within a comfortable safety margin,” OceanGate said in its court filing.

It weighs 20,000 pounds in the air, but is ballasted so it can float neutrally once it reaches the ocean floor, the company says.

Titan is made of “titanium and filament wound carbon fiber” and has been shown to “withstand the immense pressures of the deep ocean,” said OceanGate.

OceanGate told the court that the Titan's viewport was “the largest of any deep-sea submarine” and that its technology provided “unrivaled views” of the deep ocean.