Investigations under way into loss of Titan sub as questions grow over its design

Concerns raised over craft's safety standards and lack of certification as US Navy reports likely implosion

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Investigations are under way into the loss of the Titan submersible, which is thought to have imploded on its dive to the Titanic wreck site on Sunday, killing all five crew members, as questions grow about the craft's experimental design, safety standards and lack of certification.

Hopes of finding the men alive were dashed on Thursday when the US Coast Guard said that debris consistent with the catastrophic loss of the pressure chamber" had been found by a remotely operated vehicle (ROV) scouring the seabed near the Titanic wreck site 400 miles (645km) south of St John's, Newfoundland.