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An aircraft detected sounds at 30-minute intervals from the area where a deep-diving tourist submersible was lost near the Titanic wreckage with five passengers, internal communications records unmasked.

Concurrently, the US Coast Guard affirmed "underwater noises" heard in the missing sub-search.

Rescuers using sonar Tuesday to search for the missing Titanic submersible with five people onboard detected underwater "banging" sounds in the North Atlantic where the craft vanished two days earlier, media reports said, citing US government communications.

A Canadian P-8 aircraft involved in the search "heard banging sounds in the area every 30 minutes. Four hours later additional sonar was deployed and banging was still heard," said an internal email sent to US Department of Homeland Security officials, according to Rolling Stone magazine.

CNN also reported that sonar picked up banging sounds, according to an internal US government memo, but that the document did not clarify when the noises were heard Tuesday, for how long, or what might have caused them.

It is worth noting that a search and rescue effort was dispatched Monday morning according to the Boston Coastguard, with both US and Canadian coastguards participating in the extensive search.

“RCC Halifax launched a P8, Poseidon, which has underwater detection capabilities from the air,” the Department of Homeland Security e-mails said.

“The PH deployed sonobuoys, which reported contact in a position close to the distress position. The P8 heard banging sounds in the area every 30 minutes. Four hours later additional sonar was deployed and banging was still heard,” it added.

The reason for the pounding noises is still unknown, as per reports.

The email added that “the Joint Rescue Coordination Centre is working to find an underwater remote-operated vehicle through partner organizations to possibly assist."

The sounds were referenced in another email received on Tuesday afternoon by The Explorers Club President Richard Garriot de Cayeux, which was acquired by Rolling Stone.

“It is being reported that at 2 am local time on site that sonar detected potential ‘tapping sounds’ at the location, implying crew may be alive and signalling,” it read.

“We have much greater confidence that 1) There is cause for hope, based on data from the field — we understand that likely signs of life have been detected at the site,” de Cayeux said in a post on social media.

According to authorities, the 21-foot vessel "Titan" lost contact with the surface less than two hours into its descent.

OceanGate Expeditions began transporting small crews of "citizen scientists" in a five-person mini-sub for $125,000 per person two years ago. Oceangate had scheduled an eight-day, seven-night excursion to the disaster for June 12-20, according to the company's website. Six tourists had planned to leave and return to St John's, Newfoundland, Canada.

Media reports say the passengers aboard are British millionaire Hamish Harding, Pakistani businessman Shahzada Dawood and his son Suleiman, and French explorer Paul-Henri Nargeolet, as well as Stockton Rush, CEO of OceanGate, the company that operates the vessel.

The sub explores the wreck, which is located on the ocean floor at 12,500 feet of water about 370 miles off the coast of Newfoundland.