A submarine used to take people to visit the Titanic, stranded in the Atlantic Ocean, has gone missing.
Boston Coastguard told BBC News that a search and rescue operation was underway off the coast of Newfoundland.
It is not clear how many people were on board when it went missing.
Small submarines occasionally take paying tourists and experts to see the wreck of the Titanic, about 3,800 m (12,500 ft) below the ocean’s surface.
OceanGate Expeditions, a private company that organizes deep-sea expeditions, confirmed in a statement that it owned the missing submarine and that people were on board.
“We are exploring and mobilizing all options to bring the crew safely,” it said on Monday. “Our entire focus is on the crew and their families on board the submarine.”
“We are working for the safe return of the crew,” it added.
The company charges guests $250,000 (£195,270) to see the famous wreck on its eight-day cruise.
It describes cruising in its carbon-fiber submersible as “a chance to step out of everyday life and discover something truly extraordinary.”
According to its website, one expedition is underway, and two more are planned for June 2024.
The company says the submersible can seat five people, usually including a pilot, three paying guests and what it calls a “content specialist.”
A full dive to the wreck, including descent and ascent, takes a total of eight hours.
Titanic lies 3,800 m (12,500 ft) at the bottom of the Atlantic Ocean. It is 600 km (370 mi) off the coast of Newfoundland, Canada.
During her maiden voyage from Southampton to New York in 1912, the passenger liner, the largest ship at the time, hit an iceberg. Of the 2,200 passengers and crew on board, more than 1,500 died.
The Titanic has been extensively researched since its discovery in 1985.
It consists of two parts, the bow and stern, separated by about 800 m (2,600 ft). A large debris field surrounds the wrecked ship.