According to this report no explosion has been detected which would rule out at least the bomb theory if the source is correct
http://www.nytimes.com/2014/03/09/wo...t.html?hp&_r=0
And for the guys who believe in a sinister hijacking plot flying below radar to Dr No island or another movie plot.... How do you escape from PSR detection between FL350 and near surface? I don't think there is a stealth version of 772 and getting from FL350 to a height where PSR does not detect you should take quite some time if you want to keep. Airframe intact.