Neither government officials nor the company that owns the five-person submersible vessel that disappeared while taking adventurers on a trip to see the wreckage of the RMS Titanic, has released the names of the people who are onboard the sub, but social media posts are offering clues as to their identities.

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The five left for the trip to explore the wreckage of the Titanic on Sunday morning aboard a submersible called Titan on a trip that is run by OceanGate, a California company. None of the five have been heard from since about an hour and 45 minutes into the descent. U.S. and Canadian military resources are searching in the area the submersible was last known to be.

Family members, businesses and friends have taken to social media to post message of thanks and to ask for prayers for the people on Titan.

Here is what we know about the passengers now:

Hamish Harding

Jannicke Mikkelsen, a Norwegian explorer, who is a friend of Harding, told CNN Tuesday morning that Harding is in the submersible.

Harding, 58, is a businessman, pilot and explorer. He is chairman of Action Aviation, a sales and air operations company based in Dubai.

Harding is no stranger to adventure and exploration. He has flown to space on a flight organized by Blue Origin, and he holds three Guinness World Records, including one for the longest time spent in the deepest part of the ocean on a single dive.

“I am proud to finally announce that I joined @oceangateexped for their RMS TITANIC Mission as a mission specialist on the sub going down to the Titanic,” Hamish Harding recently wrote on his Instagram page.

Shahzada Dawood, Suleman Dawood

The Pakistani businessman Shahzada Dawood, 48, and his son, Suleman, 19, are on the Titan, according to their family.

According to the BBC, In a statement released on Tuesday, the Dawood family said the two 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,” it said. “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 while granting the family privacy at this time.”

Shahzada is the vice chairman of the Dawood Hercules Corporation, part of the Dawood Group, a conglomerate of various businesses owned by the family.

According to the company website, Shahzada lives with his wife, Christine, and his children, Suleman and Alina.

Paul-Henry Nargeolet

Paul-Henry Nargeolet, 77, is a former French Navy diver. According to the BBC, Mathieu Johann, a spokesperson who has been in touch with his daughter Chloé Nargeolet, said he hoped Nargeolet’s composure and military career would reassure the crew on board, even if the operation’s outcome did not depend on him.

Nargeolet is the director of underwater research at a company that owns the rights to the Titanic wreck. A co-worker confirmed to CNN that Nargeolet is on the sub.

Stockton Rush

The chief executive of OceanGate, Stockton Rush, 73, is widely reported to be on the vessel, though neither family nor OceanGate has confirmed that.

Rush founded OceanGate in 2009. The company is described as “an ocean exploration venture focused on providing crewed submersible services to enable researchers and explorers to access the oceans’ vast resources.”

At the age of 19, Rush became the youngest jet transport-rated pilot in the world after obtaining his DC-8 Type/Captain’s rating at the United Airlines Jet Training Institute in 1981.

He graduated with a degree in aerospace engineering from Princeton University and earned a master’s degree drome the UC Berkeley Haas School of Business.

“It is an amazingly beautiful wreck,” Rush told Britain’s Sky News of the Titanic earlier this year. “You can see inside, we dipped down and saw the grand staircase and saw some of the chandeliers still hanging.”