The  submersible was diving 13,000 feet to view the Titanic which is located on the ocean floor.

“This is an incredibly unforgiving environment down there on the sea floor and the debris is consistent with a catastrophic implosion of the vessel,” US Coast Guard Rear Adm. John Mauger, the First Coast Guard District commander, told reporters as quoted by CNN.

Tour organizer OceanGate Expeditions said in a statement: "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."

"These men were true explorers who shared a distinct spirit of adventure, and a deep passion for exploring and protecting the world’s oceans. Our hearts are with these five souls and every member of their families during this tragic time. We grieve the loss of life and joy they brought to everyone they knew," read the statement.

"This is an extremely sad time for our dedicated employees who are exhausted and grieving deeply over this loss," the statement said.

The US Coast Guard said in a statement: "A remotely operated vehicle (ROV) discovered a debris field Thursday, approximately 1,600 feet off the bow of the Titanic."

"The ROV deployed to the Canadian vessel Horizon Arctic, discovered the tail section of the 21-foot submersible, Titan, that went missing Sunday," the statement said.