The Titan submersible implosion that killed all five passengers was heard by a top-secret US Navy acoustic detection system hours after it began its doomed descent to the Titanic wreck, according to a report.

The Navy began using the system, which is used to locate enemy submarines, to listen for the Titan almost immediately after it lost contact with its radio ship on Sunday, a US defense official told The Wall Street Journal.

Shortly after the Navy began listening, they heard what they believed to be an implosion coming from the area where debris from the vessel was found on Thursday.

“The US Navy conducted an analysis of acoustic data and detected an anomaly consistent with an implosion or explosion in the general vicinity of where the Titan submersible was operating when communications were lost,” a senior official told the outlet.

“While not definitive, this information was immediately shared with the Incident Commander to assist with the ongoing search and rescue mission,” they added.

OceanGate’s Titan submersible — a cramped, 22-foot long vessel piloted by a gaming controller — lost communications around one hour and 45 minutes into its eight-hour descent to the Titanic wreck site, which sits about 12,500 feet below the surface roughly 900 miles off the coast of Newfoundland.

At some point, the vessel imploded under the immense pressure of the Atlantic, instantly killing everyone on board, according to United States Coast Guard officials. 

The disappearance of the craft sparked a frantic international search, as Titan’s remaining oxygen supply quickly depleted.

On Thursday, five major pieces of debris were spotted by a remotely operated vehicle [ROV] 1,600 feet from the Titanic shipwreck, with the debris being “consistent with the catastrophic loss of [Titan’s] pressure chamber,” Coast Guard Rear Adm. John Mauger told reporters.

Mauger said that throughout the 72-hour search sonar buoys deployed in the ocean had “not detected any catastrophic events” indicating the vessel imploded.

Those who were killed were OceanGate CEO Stockton Rush, who piloted the vessel, British billionaire explorer Hamish Harding, French Titanic expert Paul-Henri Nargeolet and Pakistani business tycoon Shahzada Dawood and his 19-year-old son, Suleman.