Who Knows if icing was involved.
But will we ever learn?
Off thread, but a coleague who went for an interview with a certain low cost carrier was asked by the human resources type person. What he would do if he found ice on his a/c in the morning. He replied de-ice it! Answer from human resources Do you know how much it costs to de-ice a 737, why not wait untill the sun comes up and melts the ice. His comment I know how much it costs to de-ice a 747 and whats that got to do with it? He got up and walked out.
So whilst company's are actively promoting this kind of thing accidents will still be happening due to ice contamination.