In reply to Gordon Stainforth:
There's a thread on PPRuNe (Professional Pilots Rumour Network) about it at the moment. Always worth a read when something like this happens, as it usually contains a lot of very informed comment.
There are a number of suggestions like that, of a cabin pressure failure, an initial emergency descent and then a loss of control. However there are also others. I'd imagine we will find out fairly soon, though, as the flight recorders should be fairly easy to locate as it's an on-land crash.
Neil