Robin400,
If there were "sparks" and "bangs", as reported, then the idea of intermittent pulses of fuel making it into the engine and igniting roughly and inefficiently on still hot turbine components seems reasonable. But these "sparks" would only need to come from one stopped engine. The reported "quiet" would indicate two stopped engines? Could "sparks" also be the reflection of a strobe from the yellow upper parts of a helicopter doing something unusual?
Ingesting something could presumably do the same, causing stalls and burps.
Falcon900,
The substantial damage to the cabin in the salvage photos looks inconsistent with having just missing a gentle landing. I'm sure the impact speed will ultimately be very clear from the wreckage. Many witnesses, including very-promptly-interviewed ones, also say that they saw the aircraft "drop" from above the height of nearby multi-story buildings. There's sure to be a good radar trace for initial height (right?) and perhaps a history of the position of onboard GPS devices. I have no doubt that this issue will ultimately be resolved accurately.
I tend to agree with the skateboard view. More information is required and to be synthesized.