'Underwater noises' detected in missing sub search: US Coast Guard

"Canadian P-3 aircraft detected underwater noises in the search area. As a result, ROV (remotely operated vehicle) operations were relocated in an attempt to explore the origin of the noises," the US Coast Guard's First District said on its official Twitter page.

The ROV searches "have yielded negative results but continue," the military branch said, adding that data from the Canadian aircraft had been shared with US Navy experts to inform future search plans.

The announcement is the most encouraging sign yet that the tourists who were en route Sunday to visit the wreckage of the Titanic in a 21-foot (6.5-meter) minisub might still be alive, as rescue teams race to reach them before their air supply runs out.

US and Canadian coast guard ships and planes are scouring 7,600 square miles (20,000 square kilometers) of ocean -- larger than the US state of Connecticut -- for the vessel, which was attempting to dive some 400 miles off the coast of Newfoundland, Canada.

Shortly before the Coast Guard tweet, Rolling Stone magazine quoted an internal email sent to US Department of Homeland Security officials saying a Canadian plane involved in the search "heard banging sounds in the area every 30 minutes."

The submersible, named Titan, was carrying three fee-paying passengers: British billionaire Hamish Harding, Pakistani businessman Shahzada Dawood, and his son Suleman.

OceanGate Expeditions chief executive Stockton Rush and French submarine operator Paul-Henri Nargeolet were also onboard.

Harding and Nargeolet are both members of The Explorers Club, a group which supports scientific expeditions.

"There is cause for hope, based on data from the field -- we understand that likely signs of life have been detected at the site," The Explorers Club said in a statement.

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