An underwater noise detected by a Canadian military plane was giving added impetus to the desperate search Wednesday for five people missing in a submersible in a remote area of the Atlantic Ocean near the wreck of the Titanic.

The U.S. Coast Guard said an Aurora patrol aircraft picked up the sound, but officials added that it was unclear what it indicated. 

The development offered a faint glimmer of hope as time became critical for the crew of the Titan, with less than a day's worth of air supply estimated to remain on the 6.4-metre vessel.

In a tweet, the coast guard said three vessels arrived at the scene early Wednesday, including the Canadian Coast Guard Ship John Cabot, which has side-scanning sonar.

Canada’s Fisheries Minister Joyce Murray told reporters in Ottawa she couldn’t speculate on the source of the noise.

”There have been sounds that have been picked up, and that just means that we will continue to double down and figure out where the submersible is and how it can be brought to the surface,” Murray said. “I think we have to retain hope as part of what we are doing as a human community to find the explorers and bring them to safety.”

The U.S. Coast Guard said an underwater robot was moved to the area where the noise was heard, but the initial searches "yielded negative results."

Murray said the sonar capability aboard the John Cabot would give the searchers “another tool to potentially find and bring back the submersible.”

The Titan lost contact with its surface launch ship Polar Prince during its descent Sunday in deep waters about 700 kilometres south of St. John’s, N.L.

On board were Stockton Rush, the CEO of OceanGate Expeditions, which owns the submersible; British businessman Hamish Harding; Pakistani nationals Shahzada Dawood and his son Suleman; and French explorer and Titanic expert Paul-Henry Nargeolet.

In addition to the John Cabot, the U.S. Coast Guard said two other vessels, the Skandi Vinland and the Atlantic Merlin, had reached the scene and were conducting search patterns.

On Tuesday U.S. Coast Guard Capt. Jamie Frederick said the Deep Energy, a Bahamas-flagged cable layer, was conducting an underwater search with its remotely operated vehicle, or ROV. The ROV has limited capability but does have a camera, Frederick said.

OceanGate has led expeditions to the Titanic wreck site for three years. The luxury liner struck an iceberg and sank in 1912, killing all but about 700 of the roughly 2,200 passengers and crew.

This report by The Canadian Press was first published June 21, 2023.