U.S. and Canadian rescue teams were searching Monday for a submersible carrying five people to the wreckage site of the Titanic after the submarine vanished deep in the Atlantic Ocean with four days’ or less worth of survival capability.

The U.S. Coast Guard in Boston is leading the search for the missing watercraft, which the Joint Rescue Coordination Centre in Halifax, Nova Scotia, said was reported overdue Sunday night about 435 miles south of St. John’s, Newfoundland.

Rear Adm. John Mauger, commander of the First Coast Guard District, said two aircraft each from the U.S. and Canada were involved in the search, along with a commercial ship, and that further assets will be added as the pursuit continues into the night.

The operation’s location − about 900 miles east of Cape Cod and up to 13,000 feet deep − complicates the task, as does the need to look both on the surface of the water and below, he said.

“It is a challenge to conduct a search in that remote area,” Mauger said at a news conference, “but we are deploying all available assets to make sure that we can locate the craft and rescue the people on board.”

Contact lost with five crew members

The Coast Guard tweeted that the 21-foot submersible named “Titan,” which left from St. John’s, began its dive Sunday morning. The Polar Prince, the Canadian ship supporting the watercraft, lost contact with it about an hour and 45 minutes later.

OceanGate Expeditions, a Washington-based deep-sea exploration company, confirmed in a statement that it owned the submersible − a vessel in the submarine family but smaller and less self-sufficient than the classic military sub.

The company’s expeditions to the Titanic wreck site include archaeologists and marine biologists. OceanGate also brings people who pay to come along, known as “mission specialists.”

FILE - This undated photo provided by OceanGate Expeditions in June 2021 shows the company's Titan submersible. On Monday, June 19, 2023, a rescue operation was underway deep in the Atlantic Ocean in search of the technologically advanced submersible vessel carrying five people to document the wreckage of the Titanic, the iconic ocean liner that sank more than a century earlier. (OceanGate Expeditions via AP, File) ORG XMIT: NYSB151

They take turns operating sonar equipment and performing other tasks in the five-person submersible. The Coast Guard said Monday there was one pilot and four “mission specialists” aboard.

“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,” OceanGate said. “We are working toward the safe return of the crewmembers.”

Based on the company’s information, Mauger said the submersible has a 96-hour emergency sustainment capability, which would include oxygen and fuel. “So we anticipate that there’s somewhere between 70 and the full 96 hours available at this point,” he said.

The Polar Prince ship, seen here while moored in Vancouver, British Columbia, Oct. 23, 2017, was monitoring a submersible Sunday but lost contact less than two hours after it dived in. A search is underway Monday for the 21-foot watercraft, which carries people to view the wreckage of the Titanic. Unlike submarines that leave and return to port under their own power, submersibles require a ship to launch and recover them. OceanGate hired the Polar Prince to ferry dozens of people and the submersible craft to the North Atlantic wreck site. (Darryl Dyck/The Canadian Press via AP) ORG XMIT: BCPS201 (Credit: DARRYL DYCK, AP)

See the Titanic in whole new way:Full-sized, 3D digital scan shows scale of wreckage site

British tourist on board

OceanGate adviser David Concannon told The Associated Press the company lost contact with the submersible Sunday morning.

Concannon, who said he planned to go on the dive but had to cancel because of a matter regarding another client, said officials are rushing to get to the site a remotely operated vehicle that can reach a depth of 20,000 feet. The Titanic wreckage is believed to lie 12,500 feet deep.

Action Aviation said its company chairman, British businessman Hamish Harding, was one of the travelers on board. The experienced adventurer went into space on Blue Origin’s New Shepard rocket last June.

Hamish Harding attends Living Legends Of Aviation Awards at The Beverly Hilton on January 20, 2023 in Beverly Hills, California.

“Every attempt is being made for a rescue mission,” Mark Butler, the company’s managing director, told the AP. “There is still plenty of time to facilitate a rescue mission. There is equipment on board for survival in this event. We’re all hoping and praying he comes back safe and sound.”