All kinds of information can be gleaned from even wreckage as devastating as this.
You don't need intact human remains to reveal telltale signs of: hypoxia, cardiac infarction, stroke, smoke inhalation. Small pieces of tissue can retain such indications.
A chemical explosion will likely leave combustion residues not found with a simple "physical" decompression. And any kind of explosive disassembly of part or all of the airframe can leave distortions different from simple impact.
Distortion vs. breakage of the tungsten filaments in indicator/warning lights can determine if they were on (hot and malleable) or off (cold and brittle) at the time of impact. Instrument dials may be "frozen" with the readings at the time of failure.
If you add up the parts and find anything missing, you can backtrack along the flight route and see if it departed the airframe prior to, or during descent.
Not that this investigation will be as easy as some, but experienced investigators know how to find the most obscure evidence.
Last edited by pattern_is_full; 12th Dec 2012 at 19:29.