Rescue teams were racing on Wednesday to trace the origin of sounds heard from the depths of the North Atlantic in a search for a tourist submersible with five people on board that vanished on its descent to the century-old wreck of the Titanic.

The U.S. Coast Guard said remotely operated vehicle (ROV) searches were deployed in the area where Canadian aircraft detected the undersea noises using sonar buoys on Tuesday. Estimates suggest the submersible’s air supply could run out by Thursday morning.

“We don’t know the source of that noise,” U.S. Coast Guard Rear Admiral John Mauger told CBS on Wednesday. Two ROVs and a surface vessel are being used to try to locate the source, he said.

“This is an incredibly complex site,” Mauger said, noting that metal and other objects under the water made it difficult to determine the source.

Even if the submersible is located, retrieving it presents huge logistical challenges, given the extreme conditions miles below the surface.

Teams from the United States, Canada and France have searched more than 10,000 square miles (25,900 square km) of open sea, roughly the size of Lebanon or the U.S. state of Massachusetts.

The 22-foot (6.7-meter) submersible Titan, operated by U.S.-based OceanGate Expeditions, began its descent at 8 a.m. (1200 GMT) on Sunday, according to the U.S. Coast Guard. It lost contact with its parent surface vessel during what should have been a two-hour dive to the Titanic.

The U.S. Coast Guard said on Tuesday at about 1700 GMT that it had enough air left for 41 hours, based on its specifications, which would mean a deadline of roughly 1000 GMT (6 a.m.) on Thursday. But experts say the air supply depends on a range of factors, including whether the submersible remains intact and still has power.

The wreck of the British ocean liner, which sank when it hit an iceberg on its maiden voyage in 1912, lies on the seabed at a depth of about 12,500 feet (3,810 meters). It is about 900 miles (1,450 km) east of Cape Cod, Massachusetts, and 400 miles south of St. John’s, Newfoundland.

Those aboard the submersible, the highlight of a tourist expedition that costs $250,000 per person, included British billionaire and adventurer Hamish Harding, 58, and Pakistani-born businessman Shahzada Dawood, 48, with his 19-year-old son Suleman, who are both British citizens.

French explorer Paul-Henri Nargeolet, 77, and Stockton Rush, founder and chief executive of OceanGate Expeditions, were also reported to be on board.

A friend of Harding, Jannicke Mikkelsen, who has accompanied the British entrepreneur on other expeditions, told Reuters on Tuesday she was hoping for good news but was not optimistic. “It would be a miracle if they are recovered alive,” she said.


Questions about the safety of the Titan were raised in a 2018 lawsuit filed by OceanGate’s former director of marine operations, David Lochridge, who claimed he was fired for voicing concerns that the hull could not withstand extreme depths.

In its own court claim against Lochridge, OceanGate said he refused to accept the lead engineer’s assurances and accused him of improperly sharing confidential information. The two sides settled their court case in November 2018.

Neither the company nor Lochridge’s attorney have commented on the details of the dispute.

Months prior to the suit, a group of submersible industry leaders wrote to OceanGate warning that the “experimental” approach” to the sub’s development could result in “minor to catastrophic” problems, the New York Times reported.

Aaron Newman, a former Titan passenger who knows some of the missing people, told NBC on Wednesday that he felt safe during his dive.

“Obviously, this is the type of exploration that’s doing things – this is not a Disney ride,” he said. “We’re going places that very few people have been.”

A French research ship carrying a deep-sea diving robot submersible was dispatched to the area at the request of the U.S. Navy and was expected to arrive later on Wednesday.

The unmanned robot is capable of diving as deep as the Titanic wreck and could help free the submersible if it is stuck, though the robot cannot lift the 21,000-pound (9,525 kg) Titan on its own.

U.S. Coast Guard said Canadian Lockheed P-3 Orion aircraft, which have sub-surface surveillance gear, detected the underwater noises on Tuesday.

Remote undersea equipment was deployed in the area and data from the aircraft was shared with U.S. Navy experts “for further analysis which will be considered in future search plans,” the U.S. Coast Guard wrote on Twitter.

It did not give details about the nature of the sounds, but CNN and Rolling Stone magazine, citing internal U.S. government communications, reported Canadian aircraft detected banging sounds at 30-minute intervals.

If Titan is stuck on the ocean floor, a rescue effort would require specialized equipment because of the massive pressures and total darkness at a depth of more than 2 miles. Titanic expert Tim Matlin said it would be “almost impossible to effect a sub-to-sub rescue” on the seabed.

The sinking of the Titanic, which killed more than 1,500 people, has long been immortalized in books and films. Popular interest was renewed by the 1997 blockbuster movie “Titanic”.