A search and rescue operation has been launched in the wake of the disappearance of a submersible that was being used to ferry tourists to the Titanic wreck.
An operation to find it was underway, the Boston Coastguard reported to the BBC on Monday.
The number of passengers, if any, on board at the time it vanished is unknown.
Small submersibles occasionally transport paying visitors and professionals to the Titanic's wreck.
The cost of multi-day excursions to the wreck is in the tens of thousands of dollars, and a dive to Titanic is said to take about eight hours to complete, including the ascent and descent.
The renowned shipwreck is located 3,800m (12,500ft) below the surface of the Atlantic. It is situated roughly 600 km (370 miles) off the Canadian province of Newfoundland.
In 1912, while traveling from Southampton to New York for the first time, the passenger liner—the biggest ship at the time—caught an iceberg. More than 1,500 people died out of the 2,200 passengers and crew on board.
Since the wreck of the Titanic was found in 1985, it has been extensively explored.
