A search and rescue effort is underway for a tourist submersible vessel that went missing in the north Atlantic while on a dive to observe the wreckage of the Titanic.
The missing vessel is believed to be OceanGate's Titan submersible, a truck-sized sub that holds five people and usually dives with a 96-hour emergency supply of oxygen.
The US Coast Guard said that contact with the sub was lost about an hour and 45 minutes into its journey. But who are the people on board?
Latest updates
Hamish Harding's family 'grateful' for support
The family of British billionaire Hamish Harding has said they are "very grateful for all the kind messages of concern and support". A statement released Action Aviation, the private plane firm chaired by Hamish, released a statement saying his family and company are "thankful for the continued efforts of the authorities and companies that have stepped in to aid in the rescue efforts".
"We put great faith and trust in their expertise."
The statement added: "The team at Action Aviation are extremely proud of Hamish and we look forward to welcoming him home."
READ: Who is UK billionaire Hamish Harding? From Antarctic explorer to space tourist
UK Foreign Office in contact with families of British citizens
The UK Foreign Office has confirmed it is in contact with the families of British citizens Hamish Harding and Shahzada Dawood and his son Sulaiman Dawood.
In a statement, the Foreign Office said: "We are in contact with the families of three British nationals following a submersible going missing off the coast of North America and are in touch with the local authorities."
The UK's foreign secretary James Cleverly appeared at a joint press conference with his US counterpart, Antony Blinken, where he said: "We wish them all the luck, and of course we hope that they will be swiftly found and returned to their loved ones."
Prime Minister Rishi Sunak shares statement
Prime Minister Rishi Sunak issued a statement regarding the missing vessel. His official spokesman said: "The families involved will be deeply concerned and his thoughts are with them and the Foreign Office is providing support," adding that Rishi "clearly wants to pass on his thanks to those that are responding" to the situation.
Dawood family statement
The Dawood family released a statement about the missing father and son, Shahzada and Sulaiman. "We are very grateful for the concern being shown by our colleagues and friends and would like to request everyone to pray for their safety."
Billionaire Hamish Harding's recent Instagram post warns of bad weather
British Billionaire Hamish Harding, who is one of the passengers aboard the missing vessel, shared an Instagram post about the dive and warned of volatile weather conditions. "Due to the worst winter in Newfoundland in 40 years, this mission is likely to be the first and only manned mission to the Titanic in 2023," he wrote on Sunday. "A weather window has just opened up and we are going to attempt a dive tomorrow."
OceanGate Expeditions responds
OceanGate Expeditions released a statement saying it is "exploring and mobilizing all options to bring the crew back safely".
Who are the five people on the submarine?
Five people embarked on the dive to see the Titanic debris with tour company, OceanGate Expedition, which offers an eight-day mission costing $250,000 per person.
The US Coast Guard said there was one pilot and four "mission specialists" aboard. So, who are they?
Hamish Harding
British businessman and explorer Hamish Harding is one of the five people on the dive. The billionaire adventurer, who has previously travelled on the Challenger Deep to the bottom of the ocean, is the chair of aviation sales and operations company Action Aviation and is also a jet pilot.
Hamish, 58, holds 16 air speed records, including a Guinness world record for the longest time spent traversing the deepest part of the ocean on a single dive.
The Cambridge-educated explorer, who is based in the United Arab Emirates, also became the first Briton to travel on Jeff Bezos' Blue Origin's fifth human spaceflight mission.
In 2016, the father-of-two joined the Apollo astronaut Buzz Aldrin on a world record-breaking expedition to Antarctica, which marked the fastest circumnavigation of the globe.
Hamish's stepson Brian Szasz confirmed that Hamish was on board the vessel when it went missing on Monday.
In a Facebook post, he wrote: "Hamish Harding, my step father, has gone missing on submarine. Thoughts and prayers.
"Thoughts and prayers for my Mom and Hamish Harding."
In a follow-up post, he added: "Thoughts and prayers for my stepfather Hamish Harding as his submarine has gone missing exploring Titanic. Search and rescue mission is underway."
Shahzada Dawood and his son, Sulaiman
British citizens Shahzada Dawood, 48, and Sulaiman Dawood, 19, who are father and son, have been confirmed to be passengers on the vessel.
Shahzada is a UK-based business advisor and board member of the Prince's Trust charity. He is also a trustee at the SETI Institute and serves as the vice chairman on the Board of Engro Corporation.
His family said in a statement: "Our son Shahzada Dawood and his son, Suleman, had embarked on a journey to visit the remnants of the Titanic in the Atlantic Ocean.
"As of now, contact has been lost with their submersible craft and there is limited information available."
Paul-Henri Nargeolet
Paul-Henri Nargelolet is reportedly onboard the vessel. Paul is a French mariner and the Director of the Underwater Research Program at Premier Exhibitions, RMS Titanic.
The 73-year-old, who served in the French Navy for 25 years, specialises in deep-diving and piloting submersibles and is a Titanic expert, having spent a lot of time at the wreck.
Back in 2019, he warned of the dangers of deep-sea voyages. "If you are 11 metres or 11 kilometres down, if something bad happens, the result is the same," the former French Naval captain told the Irish Examiner.
"When you're in very deep water, you're dead before you realise that something is wrong, so it's just not a problem."
Stockton Rush
Stockton Rush is reportedly the fifth passenger on the sub. He is the Chief Executive Officer of OceanGate, the company behind the tour which provides crewed submersibles for industry, research and exploration.
Stockton began his career as a pilot and became the youngest jet transport-rated pilot in the world at the age of 19 in 1981.
He went on to obtain a BSE in Aerospace Engineering from Princeton University in 1984, and his MBA from the U.C. Berkeley Haas School of Business in 1989.
He is also a co-founder and member of the Board of Trustees of OceanGate Foundation (2012), a "non-profit organization which aims to catalyze emerging marine technology to further discoveries in marine science, history, and archaeology," according to the company's website.