The OceanGate Expeditions company said that it was "mobilizing all options" to locate a submersible vehicle that had set out to explore the wreckage of the Titanic.
A submarine on a tourism expedition to explore the wreckage of the Titanic has gone missing off the coast of southeastern Canada, the private company that operates the vessel said on Monday.
OceanGate Expeditions said in a brief statement issued to the BBC and other media that it had lost contact with the submarine and was "mobilizing all options" to rescue those on board.
The regional branch of the US Coast Guard said on Monday that it was seeking a submersible vehicle in the Atlantic Ocean, somewhere around the site of the Titanic shipwreck.
"A US Coast Guard C-130 crew is searching for an overdue Canadian research submarine approximately 900 miles off Cape Cod," USCG Northeast said.
It said a Canadian plane with underwater detection capabilities was assisting in the search.
"The US Coast Guard is searching for a 21-foot submersible from the Canadian research vessel Polar Prince," it said a short while later, referring to Ocean Gate Expeditions' vessel. "The 5 person crew submerged Sunday morning, and the crew of the Polar Prince lost contact with them approximately 1 hour and 45 minutes into the vessel's dive."
"We are deeply thankful for the extensive assistance we have received from several government agencies and deep sea companies in our efforts to reestablish contact with the submersible," OceanGate Expeditions said.