Searchers detected underwater noises before dawn Wednesday amid their North Atlantic hunt for a submersible vessel and its five-man crew that had set out to visit the Titanic’s wreckage days earlier.

The possible clue comes as oxygen aboard the missing Titan is running dangerously low, with officials estimating the vessel has less than 24 hours’ worth of air supply remaining.

The U.S. Coast Guard said a Canadian P-3 surveillance plane picked up the sound shortly after midnight Wednesday. Authorities said remotely operated vehicles that can submerge were relocated to the area to scour it for any leads, but crews have yet to find anything.

“You have to remember that it’s the wreck site of the Titanic, so there is a lot of metal and different objects in the water around the site,” Coast Guard Rear Adm. John Mauger told CBS News on Wednesday.

Three additional ships — the Canadian coast guard’s John Cabot, the DOF Subsea’s Skandi Vinland and the Canadian supply vessel Atlantic Merlin — arrived at the sprawling search area Wednesday morning, with all three using the John Cabot’s side scanning sonar to conduct search patterns, according to officials. 

Canadian Ship Glace Bay is en route to the search area. The ship is equipped with a mobile decompression chamber and has medical personnel aboard.

Titan, a 21-foot tourism and research submersible, first made its descent toward the Titanic’s wreckage site on Sunday morning. The vessel lost contact with the surface less than two hours after its descent.

Excursion organizer OceanGate Expeditions notified the Coast Guard Sunday evening. Authorities responded by immediately launching a search effort that covers an area the size of Connecticut.

The Coast Guard is coordinating the search with the Canadian coast guard and the Canadian armed forces, but all three agencies lack the equipment to reach the deep ocean where the Titan may be stuck.

Most search efforts have involved deploying sonar buoys on the surface in hopes that a noise will be detected. Atlante, a French research ship arriving at the search area Wednesday night, has a vessel that can venture down the 2.5 miles underwater to the Titanic’s final resting place.

Aboard the Titan are OceanGate founder Stockton Rush, British explorer Hamish Harding, Titanic researcher Paul-Henri Nargeolet, and British businessman Shahzada Dawood and his 19-year-old son, Suleman.

CBS News reporter David Pogue, who rode in the Titan for a report last year, said Tuesday that hope is “quickly fading” for the missing crew.

Mr. Pogue told the network that it’s “really bad” that the Titan lost its signal during its descent. To him, that meant that something “catastrophic” took place.

• Matt Delaney can be reached at mdelaney@washingtontimes.com.