(NewsNation) — The search for a small submarine carrying a group of people touring the ship wreckage of the Titanic continued Monday night in a race against time to find the passengers lost at sea.

The missing submersible Titan, which holds up to five people onboard, carries tourists to view the Titanic’s remains about 12,000 feet at the bottom of the Atlantic Ocean off the coast of Newfoundland, Canada. The infamous ship sank in 1912 after hitting an iceberg.

It is unclear whether the tour had gotten lost or if there was an issue on board.

The U.S. Coast Guard said Monday night it would continue to do surface searches by boat “throughout the evening.”

Air searches using American C-130 planes and a Canadian P8 Poseidon were finished Monday night and will continue Tuesday morning, the Coast Guard said.

Coast Guard officials confirmed in a Monday afternoon news conference the vessel was designed for passengers to be able to survive for 96 hours in the event of an emergency. They declined to confirm the identities of those on board, pending notification of the families.

Authorities said the first focus was on locating the vessel, but that potential rescue operations were being explored in the event the missing submarine was found in the water rather than on the surface.

The Coast Guard said there was one pilot and four “mission specialists” aboard.

The Titan, owned by OceansGate Expeditions, can reach depths of more than 13,000 feet and carries five people, three of whom may be tourists. The sub has an oxygen supply which should last for four days and has a real-time monitoring system that analyzes the pressure on the hull and integrity of the vessel.

One of those on board is British businessman Hamish Harding. Before the mission launched, Harding wrote on Facebook this mission was expected to be the only manned mission to the Titanic in 2023, and they were set to launch due to a weather window that just opened up.

“We started steaming from St. Johns, Newfoundland, Canada yesterday and are planning to start dive operations around 4 a.m. tomorrow morning. Until then we have a lot of preparations and briefings to do,” Harding wrote.

In 2021, OceanGate Expeditions began what it expected to become an annual voyage to chronicle the deterioration of the iconic ocean liner that struck an iceberg and sank in 1912.

The company said at the time that in addition to archaeologists and marine biologists, the expeditions also would include roughly 40 paid tourists who would take turns operating sonar equipment and performing other tasks in the five-person submersible.

The initial group of tourists was funding the expedition by spending anywhere from $100,000 to $150,000 apiece.

The Associated Press contributed to this report.