Both CNN and the American ABC are reporting the Afghan MoTaCA has held a press conference stating the crash was a result of a load shift. From what I could make of the reports, they have found broken cargo strap buckles.
In such an impact as this, I have a hard time accepting post crash broken 'buckles' as proof of a load shift, even if on the fwd facing straps.
(I do believe it was a load shift)