Titanic Exploration Submersible Missing, Rescue Efforts Underway

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 and the U.S. Coast Guard.

OceanGate Expeditions said in a statement on Monday that it was "mobilizing all options" to rescue those on the underwater vessel, which typically has five people on board.

British billionaire Hamish Harding is among the passengers, according to a social media post from a relative.

The Coast Guard said on Twitter that a boat on the surface, the Polar Prince, lost contact with the submersible about an hour and 45 minutes after it began diving toward the wreckage site on Sunday morning.

U.S. and Canadian authorities have launched a search-and-rescue operation, including aerial and surface searches, according to statements from the Coast Guard and Canada's defense ministry.

OceanGate said, "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."

Harding's stepson wrote on Facebook that Harding had "gone missing on submarine" and asked for "thoughts and prayers." The stepson subsequently removed the post, citing respect for the family's privacy.

Harding himself had posted on Facebook a day earlier that he would be aboard the sub. There have been no posts from him since.

The expedition headed out to sea on Friday, and the first dive was set for Sunday morning, according to Harding's post.

The expeditions, which cost $250,000 per person, start in St. John's, Newfoundland, before heading out approximately 400 miles (640 km) into the Atlantic to the wreckage site, according to OceanGate's website.

In order to visit the wreck, passengers climb inside Titan, the five-person submersible, which takes two hours to descend approximately 12,500 feet (3,800 m) to the Titanic. The expedition company said that the craft has life support for its standard load of five people for 96 hours.

The British passenger ship famously sank in 1912 on its maiden voyage after striking an iceberg, killing more than 1,500 people. The story has been immortalized in nonfiction and fiction books as well as the 1997 blockbuster movie "Titanic."

(Reuters - Reporting by Joseph Ax, Kanishka Singh and Njuwa Maina; Additional reporting by Ismail Shakil; Editing by Doina Chiacu, Franklin Paul, Jonathan Oatis and Cynthia Osterman)