The five passengers on board the missing Titan submersible have died, a Coast Guard official said.
The company that operates the vessel said the five men were "true explorers who shared a distinct spirit of adventure".
The Coast Guard said that a debris field was discovered near the wreck of the Titanic earlier on Thursday morning.
The vessel disappeared on Sunday.
The men on board the sub included Stockton Rush, the 61-year-old CEO of OceanGate, as well as British-Pakistani businessman Shahzada Dawood, 48, his son Suleman, 19, and British businessman Hamish Harding, 58.
The fifth man on board, Paul-Henry Nargeolet, was a 77-year-old former French navy diver and renowned explorer.
At a news conference on Thursday, Rear Adm John Mauger of the US Coast Guard said that the debris is believed to be consistent with the Titan submersible.
It is unclear what led to the destruction of the Titan.
The disappearance of the vessel led to a massive international search effort involving US, Canadian, British and French forces.
In a statement, OceanGate said it appreciates "their commitment to finding these five explorers, and their days and nights of tireless work in support of our crew and their families".
The debris was located by a remote-controlled underwater search vehicle (ROV) about 1,600 feet (480m) from the wreckage of the Titanic.
Five separate pieces were discovered that allowed authorities to confirm they came from the Titan, including a tail cone.
Rear Adm Mauger said he did not have an answer on whether the bodies of the five men on-board were likely to be recovered.
"This is an incredibly unforgiving environment down there on the seafloor," he said.
ROV's will remain in the area as the investigation into what happened continued, Rear Adm Mauger added.