A submarine on a tourism expedition to explore the wreckage of the Titanic has gone missing off the coast of southeastern Canada, according to the private company that operates the vessel.
OceanGate Expeditions said in a brief statement on Monday that it was "mobilizing all options" to rescue those on board the vessel.
It was not immediately clear how many people were missing.
"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 said in a statement.
The company is currently operating its fifth Titanic "mission" of 2023, which was scheduled to start last week and finish on Thursday.
The expedition, which costs $250,000 per person, starts in St. John's, Newfoundland, before heading out approximately 400 miles into the Atlantic to the wreckage site.
In order to visit the wreck, passengers climb inside Titan, a five-person submersible, which takes about two hours to descend to the Titanic.
The British passenger ship sunk in 1912 on its maiden voyage after striking an iceberg, killing more than 1,500 people.

Ten dead after shooter opens fire at high school in Canada
Tropical cyclone Gezani slams into Madagascar, killing nine
Russian strike kills father and three children near Ukraine's Kharkiv
Cambodia says it has closed almost 200 scam centres in fraud crackdown
India tightens grip on social media with new takedown rule
Indonesia says proposed Gaza peacekeeping force could total 20,000 troops
Philippine Congress dismisses impeachment complaints against Marcos Jr.
UK's Starmer refuses to heed calls to quit over fallout from Epstein scandal
