The FSB said today:
No evidence or facts indicating a possibility of an act of terrorism or diversion on board of the aircraft have been found yet. We have eyewitnesses of the Tu-154 crash and a video recording is available. The main working models for the early Sunday Tu-154 crash remain a foreign object penetrating the engine, poor fuel quality leading to loss of power and engine failure, pilot error, or some other technical malfunction. According to the Minoborony, the aircraft carried no military or dual-purpose cargo or pyrotechnical devices.
26 December 2016