All five aboard a submersible missing near the wreck of the Titanic died after the vessel suffered a "catastrophic implosion" in the ocean depths, the US Coast Guard said Thursday.
The sombre announcement ended a multinational search-and-rescue operation that captivated the world since the small tourist craft went missing in the North Atlantic on Sunday.
Rear Admiral John Mauger told reporters in Boston that analysis showed that debris, found on the seafloor 1,600 feet (500 meters) from the bow of the Titanic, was consistent with the implosion of the sub's pressure chamber.
"On behalf of the United States Coast Guard and the entire unified command, I offer my deepest condolences to the families," Mauger said.
On board were British explorer Hamish Harding, French expert Paul-Henri Nargeolet, Pakistani-British tycoon Shahzada Dawood and his son Suleman, and Stockton Rush, CEO of the sub's operator OceanGate Expeditions.
OceanGate said its "hearts are with these five souls and every member of their families during this tragic time."
"These men were true explorers who shared a distinct spirit of adventure, and a deep passion for exploring and protecting the world's oceans," it said in a statement.
"We grieve the loss of life and joy they brought to everyone they knew."
The Coast Guard announced earlier on Thursday that an underwater robot had discovered a "debris field." Mauger said that it turned out to be the sub's tail cone as well as additional debris.
He declined to be drawn on whether the remains of the men would be retrieved and said the process of demobilizing personnel and vessels from the scene would soon begin.
Mauger added that unmanned robots would continue operations on the seafloor for now.
"We'll collect as much information as we can," he said, adding that he hoped the discovery might provide "some solace during this difficult time" to families.
The small sub-named Titan disappeared on Sunday as it descended to the Titanic, which sits more than two miles (nearly four kilometres) below the ocean's surface and 400 miles off the coast of Newfoundland, Canada.
OceanGate Expeditions charges $250,000 for a seat on the sub. Harding was a billionaire and keen explorer with three Guinness Records to his name. Nargeolet was nicknamed "Mr Titanic" for his frequent dives at the site.
Titanic's lure
The 21-foot (6.5-meter) Titan began its descent at 8:00 am on Sunday and had been due to resurface seven hours later.
But the craft lost communication with its mothership less than two hours into its trip.
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 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 specializes in deep water search and recovery operations, said earlier the discovery of debris indicated a rapid breakup 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 onboard, told Sky News.
In 2018, OceanGate Expeditions' former director of marine operations David Lochridge alleged in a lawsuit that he had been fired after raising concerns about the company's "experimental and untested design" of Titan.