New 'Titan' Sub Documentary Highlights Audio of Rhythmic Knocking Heard During Search

“The symmetry between those knockings is very unusual,” former Navy submarine Captain Ryan Ramsey said in the trailer

An upcoming documentary on the doomed Titan submarine features a clip of knocking sounds rescuers reportedly heard during their search back in June 2023.

In Minute by Minute: The Titan Sub Disaster, airing on the U.K.'s Channel 5 on March 6 and 7, viewers get a look into the fateful day the OceanGate submersible disappeared in the North Atlantic with five passengers aboard. 

Related: 'Titanic' Sub Passengers Died Due to 'Catastrophic' Pressure Implosion: Full Recap

A new trailer for the doc, which can be seen on British site UNILAD, contains audio revealing that there were noises resembling knocking in the search area during the rescue mission. In the newly-released clip, the documentary’s narrator recalls the hopeful reports of banging in 30-minute increments before playing the eerie audio.

“The symmetry between those knockings is very unusual,” former Navy submarine Captain Ryan Ramsey said. “It’s rhythmic, it’s like somebody is making that sound, and the fact that it is repeated is really unusual.”

At the time, in June 2023, reports of sounds by the search and rescue teams were confirmed by the U.S. Coast Guard in a statement, saying that a Canadian P-3 aircraft “detected underwater noises in the search area.”

Shortly after, U.S. Coast Guard Petty Officer 3rd Class Briana Carter told PEOPLE the notion that those noises came from inside the vessel were not true.

“We don’t have anything at this time indicating any implosion or banging,” Carter said on June 21, three days after the submarine disappeared.

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The Titan carried five passengers and was headed to the site of the sunken Titanic on June 18, 2023. It lost signals with the Canadian expedition vessel Polar Prince “approximately 1 hour and 45 minutes” into the dive.

Related: OceanGate CEO Stockton Rush Once Said He’d ‘Broken Some Rules’ in Building ‘Titan’ Sub

Per protocol, the Polar Prince conducted an initial search, but then requested assistance from the Coast Guard after failing to locate the missing vessel. Maritime law places that jurisdiction under the U.S. Coast Guard of Boston, who worked with the Canadian Coast Guard to coordinate search and rescue teams.

Aboard the submersible were Pakistani businessman Shahzada Dawood and his son Suleman Dawood, along with OceanGate CEO Stockton Rush, Titanic expert Paul-Henri Nargeolet and British billionaire Hamish Harding.

Equipped with 96 hours of oxygen, it was a race against time to find the sub and free potential survivors.

Related: Everything to Know About the 'Titanic'-Bound Sub That Went Missing

“This is a very complex search, and the unified team is working around the clock to bring all available assets and expertise to bear as quickly as possible in an effort to solve this very complex problem,” the Coast Guard captain told reporters on June 20.

On June 22, the search concluded. That day, the U.S. Coast Guard confirmed that all five people were presumed dead after they found debris that was likely caused by a "catastrophic implosion."

During that press conference, the Coast Guard said that the reports of "banging" sounds discovered earlier in the week were likely not sounds coming from the Titan, as they were not consistent with a "catastrophic implosion."

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