As I posted earlier (see below) and with all prune type focus (including film from within and external to aircraft) being on the Left Engine smoke/fire = presumed failure, it is now separately in question, yet will be part of any investigation anyway, that kerosene may have been mis-fuelled. We will know from the investigation soon enough.
Further, from external (eye witness report referenced below, who saw Right Engine on fire before impact) and now from one passenger on board (this from a chat at Wonderboom a week ago), it seems the Right Engine was failing/failed also, before impact.
Together, a double eng failure is a horrible day at the office! How it happened C O U L D be explained by fuel Octane rating, Water injection or other reasons unknown. However, that a separate suggestion of missfuelling is now in play, it is plausible that this may be involved. I’m trying to choose my words carefully, for we all know that we don’t know what we don’t know and that this .......... is a rumour mill.........
The fuel type (Avgas v Kerosene) actually pumped into wing during refuelling prior to this flight, is now in question.
It will of course be critical to see what the investigation finds from fuel samples taken.
I mention this because it now appears that both engines were failing / had failed, meaning the right engine was also seen on fire, before impact. That report from an experienced pilot eye witness on ground, close to the crash.