The Titanic submarine is 'locked from the outside' with no way to escape, according to a previous passenger.
A massive search and rescue operation is still under way in the mid Atlantic after a tourist submarine went missing during a dive to Titanic's wreck on Sunday.
David Pogue, a CBS reporter who travelled in the Titan submersible last year, told the BBC that passengers were sealed inside the vessel by bolts applied from the outside.
