I don't know any more than anybody has posted anywhere, but from the stuff I read yesterday it sounded like there was a major fire which either spread to the cockpit, incapacitating the pilot(s), or the smoke from it filled the cockpit and the ventilation system (if there was one) was not capable of being shut off so as to stop the smoke entering.
Either way, a dire situation and the sooner the details come out the better.
The AAIB report is going to take a year and most of them don't contain much useful information beyond "official" speculation.