In listening to the reports it seems to me very odd that there should be lots of people who saw this when it was 4.45am in the morning.
Sunrise in Cairo is around 0650 Local so they would have done well to see it crash let alone assess what state the aircraft was in.
There also seem to be very few factual details. ie: What time was takeoff, what time did it crash, what was the heading/altitude etc.
Not suprised at the Egyptian's discounting terrorism. Having worked in Cairo for a year it is fairly typical for them to answer "factually" with what they want the answer to be rather than what it is or could be.