A submarine used to take people to see the wreck of the Titanic has gone missing in the Atlantic Ocean, prompting a search and rescue operation.
Boston Coastguard told the BBC on Monday that a search was underway.
It is not clear how many people were on board when it disappeared.
Small submarines occasionally take paying tourists and experts to see the wreck of the Titanic.
OceanGate Expeditions, a private company that sends submarines on deep-sea expeditions, recently posted on its social media feeds that one of its expeditions was “in progress.”
The company, which has not commented on the reports, is looking at $250,000 (£195,270) per destination on its 8-day trip.
It describes cruising in its carbon-fiber submersible as “a chance to step out of everyday life and discover something truly extraordinary.”
The BBC has contacted the company for comment.
Titanic lies 3,800 m (12,500 ft) at the bottom of the Atlantic Ocean. It is about 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.