S Korea ferry: What caused the disaster?
17 April 2014 Last updated at 23:21 BST
The reason that the South Korean ferry carrying 475 passengers began listing and then sunk has not yet emerged, but the manner of the evacuation has already been criticised.
Passengers were initially instructed to remain in the cabins, and only two life boats were launched.
David Shukman examines what could have been behind the disaster, and what went wrong.