All Passengers Aboard Titanic Sub Believed To Be Dead, Says Operator: 10 Facts

The operator of the submersible, missing near the Titanic wreck said it believed that the passengers aboard the vessel "have been sadly lost".

Debris found on the ocean floor on Thursday near the wreck of the Titanic is thought to be from a missing tourist submersible, CNN reported citing an internal US Coast Guard document.

The Titan was designed to have an oxygen supply of as much as 96 hours in case of an emergency.

Among the five people aboard the missing vessel are British billionaire Hamish Harding, Pakistani tycoon Shahzada Dawood, and his son.

A Canadian plane with sonar capabilities looking for the Titan's vessel picked up sounds on Wednesday, and remotely operated vehicles were moved to the area where the noises originated.

The sounds raised hopes that the passengers on the small tourist craft are still alive though experts have not been able to confirm their source.

"When you're in the middle of a search-and-rescue case, you always have hope. With respect to the noises specifically, we don't know what they are, to be frank with you," says Coast Guard Captain Jamie Frederick.

"Sometimes you're in a position where you have to make a tough decision. We're not there yet," Captain Frederick said, adding that it remained a search-and-rescue mission "100 percent."

The operation of the missing submersible and its rescue operation's race against time has been riveting onlookers. People have been glued to their television screens, fascinated by maritime experts detailing the hurdles for rescue efforts in a vast expanse of sea.

Experts had raised safety concerns about the submersible vessel in 2018, expressing concern that OceanGate opted against certifying the Titan through third parties such as the American Bureau of Shipping, a leading classifier of submersibles.