The five passengers onboard the Titan submersible have died, the tour company behind the Titanic expedition and US Coast Guard have said.
OceanGate announced the passengers have "sadly been lost" in a statement ahead of the Coast Guard's press conference.
The statement said: "We now believe that our CEO Stockton Rush, Shahzada Dawood and his son Suleman Dawood, Hamish Harding, and Paul-Henri Nargeolet, have sadly been lost."
The company added: "Our hearts are with these five souls and every member of their families during this tragic time.
Rear Admiral John Mauger
"We grieve the loss of life and joy they brought to everyone they knew."
British billionaire Hamish Harding, Pakistani businessman Shahzada Dawood, his son Suleman Dawood, French submersible pilot Paul-Henri Nargeolet and OceanGate chief executive Stockton Rush were onboard the vessel.
The US Coast Guard provided an update at 8pm BST after debris was found near the site of the Titanic's wreckage.
Rear Admiral John Mauger said: "In consultation with experts from within the unified command, the debris is consistent with the catastrophic loss of the pressure chamber.
Royal Canadian Air Force CP-140 Aurora maritime surveillance aircraft searches for the missing OceanGate submersibleReuters
"Upon this determination, we immediately notified the families.
"On behalf of the United States Coast Guard and the entire unified command I offer my deepest condolences to the families."
Mauger was unable to confirm whether the five bodies could be recovered but said there was no connection between the reported underwater noises and the location on the sea floor.
He also revealed it is not yet known if when the implosion took place.
The Titanic tourist sub vanished in the Atlantic Ocean on Sunday, sparking an urgent searchReuters
The Titan vanished during an expedition to the Titanic's wreckage on Sunday.
Remotely operated vehicles will continue to search the depths of the Atlantic Ocean for more information.
Five pieces of debris helped rescue staff determine a "catastrophic" event had taken place involving the Titan.
The debris was found around 1,600 feet from the Titanic.