A diving craft from a company that charges $250,000 for tours of the Titanic shipwreck has gone missing in the North Atlantic with five people aboard.

“Our entire focus is on the crew members in the submersible and their families,” OceanGate Expeditions, which runs underwater vessels for charter and scientific exploration, said in a statement Monday. “We are working toward the safe return of the crew members.”

Among those missing is Hamish Harding, chairman of Action Aviation, according to Mark Butler, managing director of the Dubai-based aircraft brokerage. In a Twitter post Sunday, the company said that “the sub had a successful launch and Hamish is currently diving.”

OceanGate offers 10-day expeditions to the Titanic site providing “qualified explorers” the opportunity to join as mission specialists, who pay fees to underwrite their training and participation with the science teams exploring the legendary ship that sank in 1912 on its maiden transatlantic voyage after hitting an iceberg. The guests pay a quarter-million dollars, according to the New York Times, which first reported the rescue operation.

The search is receiving “extensive assistance” from several government agencies and deep sea companies in trying to re-establish contact with the missing submersible, according to the OceanGate statement. A company representative didn’t reply to requests for further comment.

The U.S. Coast Guard received a call Sunday from the submersible’s command ship, the Polar Prince, that it lost communications with the vessel about 900 miles east of Cape Cod, Massachusetts, according to Lt. Samantha Corcoran, a Coast Guard spokesperson in Boston. A C-130 plane with radar capability was dispatched to search the area Sunday, and on Monday was joined by a Canadian P-8 Poseidon, an aircraft designed for anti-submarine warfare.

“We’re focused on the search and hoping to safely locate all five individuals,” Corcoran said.

Everett, Wash.-based OceanGate ran expeditions to explore the wreck in 2021 and 2022, with a maximum depth of 12,500 feet, according to the firm’s website. A photo of a submersible and the Titanic dive operations was posted on its Twitter feed on June 1.

The trips consist of eight days at sea to survey the wreckage and document the sunken vessel’s condition, as well as the flora and fauna inhabiting the wreck site.

The missing submersible, the Titan, carries a pilot and four crew members to a maximum depth of 4,000 meters and has an onboard real-time system to monitor the health of passengers that provides “early warning detection for the pilot with enough time to arrest the descent and safely return to surface,” according to OceanGate’s website.