What you need to know:
- Acoustic detectors used to track enemy submarines picked up the fatal blast.
The US military originally detected the likely implosion of the craft on secret underwater sound monitoring devices shortly after it went missing on Sunday, the Wall Street Journal reported 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," an unnamed senior Navy official told the Journal.
The small sub named Titan disappeared on Sunday as it descended to the Titanic, which sits more than two miles (nearly four kilometers) below the ocean's surface and 400 miles off the coast of Newfoundland, Canada.
OceanGate Expeditions charged $250,000 for a seat on the sub. In a 2018 lawsuit, its former director of marine operations raised concerns about the "experimental and untested design" of Titan.
The Titanic International Society said it could be time to replace manned missions to the wreck with autonomous machines.
"It is time to consider seriously whether human trips to Titanic's wreck should end in the name of safety, with relatively little remaining to be learned from or about the wreck," it said in a Facebook post.
"Crewed submersibles' roles in surveying the wreck now can be assigned to autonomous underwater vehicles."
On board were British explorer Hamish Harding, French submarine expert Paul-Henri Nargeolet, Pakistani-British tycoon Shahzada Dawood and his son Suleman, and Stockton Rush, CEO of the sub's operator OceanGate Expeditions.
Harding was a billionaire and keen explorer with three Guinness Records, while the Dawoods belonged to one of Pakistan's wealthiest families. Nargeolet was nicknamed "Mr Titanic" for his frequent dives at the site.
Harding's family paid tribute to the aviation tycoon in a statement, saying he was a "passionate explorer" as well as a "loving husband and a dedicated father to his two sons."
"What he achieved in his lifetime was truly remarkable and if we can take any small consolation from this tragedy, it's that we lost him doing what he loved," the family said.
The Dawoods' loved ones also expressed their "profound grief" at their loss in a brief statement.
"We are truly grateful to all those involved in the rescue operations. Their untiring efforts were a source of strength for us during this time," read the statement.
The British and Pakistani governments expressed their "deepest condolences" to all the men's families.
The 21-foot (6.5-meter) Titan had been due to resurface seven hours after beginning its descent at 8am on Sunday.
But the craft lost communication with its mothership less than two hours in.
Ships and planes from the US and Canadian coast guards, as well as a robot sent from France, scoured 10,000 square miles (around 20,000 square kilometres) of surface water — roughly the size of the US state of Massachusetts — for the vessel.
The search honed in on areas where underwater banging noises were detected late Tuesday and Wednesday. But Mauger said that ultimately the sounds did not appear to have any relation to the site of the debris.
The Titanic hit an iceberg and sank in 1912 during its maiden voyage from England to New York with 2,224 passengers and crew on board. More than 1,500 people died.
It was found in 1985 and remains a lure for nautical experts and underwater tourists.
The pressure at that depth as measured in atmospheres, is 400 times what it is at sea level.
Marine scientist and oceanographer David Mearns, who specialises in deep water search and recovery operations, said earlier the debris discovery indicated a rapid break-up of the submersible.
"The only saving grace about that is that it would have been immediate, literally in milliseconds, and the men would have had no idea what was happening," Mearns, who was friends with two of those on board, told Sky News.