UK billionaire Hamish Harding is one of five people on board a missing tourist submersible used to take people to see the wreck of the Titanic.
Sky News understands two others on board the vessel, named Titan, are French submersible pilot Paul-Henry Nargeolet, and chief executive and founder of OceanGate Expeditions Stockton Rush.
The US Coast Guard said the 21ft vessel has five people on board and warned that the search, taking place approximately 900 miles east off Cape Cod, has been "challenging" due to the remote location.
