A submarine carrying tourists to explore the wreckage of the Titanic went missing off the coast of southeastern Canada on Sunday. The U.S. Coast Guard and Canadian ships and planes have been searching for the sub, which is capable of staying underwater for 96 hours.

The sub called the Titan, was carrying one pilot and four passengers when it lost contact with the surface about one hour and 45 minutes after it began diving toward the Titanic’s wreckage. The passengers include British billionaire Hamish Harding.

The Coast Guard said it is deploying all available assets to find the sub and rescue the people on board. Officials have also been reaching out to commercial vessels for help.

The company that operates the sub, OceanGate Expeditions, said it is “mobilizing all options” to rescue those on board.

• The Titanic 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.”
• The search area is about 900 miles (1,450 km) east of Cape Cod.
• The sub is equipped with sonar buoys that can monitor to a depth of 13,000 feet (3,962 meters).
• The expedition to the Titanic’s wreckage costs $250,000 per person.
• The Titanic’s wreckage is located at a depth of about 12,500 feet (3,800 m).