A submersible operated by the company OceanGate Expeditions that was diving to see the wreck of the Titanic went missing on Sunday (June 18), and rescuers are now searching for the vessel.

Five people were on-board, including British billionaire Hamish Harding, as well as CEO of the company Stockton Rush.

OceanGate said in a statement that it was "exploring and mobilising all options" to bring the crew back safely.

It is understood that the Titan craft has a 96-hour oxygen supply in case of emergencies - meaning only around two days of "life support" remain, Sky News reports. 

OceanGate Expeditions have come to worldwide attention over this incident, but who are they and when did they start running the Titanic tours?

What we know about OceanGate Expeditions

On its website, OceanGate describes itself as a privately owned company located in the city of Everett in the state of Washington.

It adds: "Since the founding of the company in 2009, the OceanGate crew has focused on increasing access to the deep ocean through innovation of the next generation of crewed submersibles and launch platforms.

"Our fleet of five-person submersibles are capable of reaching depths as deep as 4,000 meters and provide unique platforms for exploring the deep ocean."

The company has successfully completed over 14 expeditions and over 200 dives in the Pacific, Atlantic and Gulf of Mexico.

Among those OceanGate had successful expeditions to the wreck of the Titanic in 2021 and 2022, which it will "continue to return annually to further document the Titanic and its rate of decay".

OceanGate Titanic submarine tours prices

The main purpose of the OceanGate Titanic expeditions is to "collect images, videos, laser, and sonar data will allow objective assessment of the rate of decay and documentation of the process".

People also have the opportunity to pay to be on the tour, which Sky News reports as costing $250,000 (£195,270) per person for the eight-day expedition.

The OceanGate website adds: "Qualified explorers have the opportunity to join the expedition as Mission Specialist crewmembers whose Training and Mission Support Fees underwrite the mission, the participation of the science team, and their own training.

"Each team of 6 Mission Specialists will join the expedition for a 10-day mission (8 Days at Sea). The entire expedition is comprised of 5 mission legs."

The Titanic wreck is located approximately 380 nautical miles south of Newfoundland, 3,800 metres underneath the surface of the sea.