NEW : The bus was not speeding at the time of the crash , a Swiss prosecutor says . NEW : The impact was so great that their seat belts did not save the children , he says . Belgian Prime Minister : " I am shocked by this accident and deeply saddened to learn about it. The bus was returning to Belgium from a ski trip with 52 people aboard , most of them children .
NEW : The bus was not speeding at the time of the crash , a Swiss prosecutor says . NEW : The impact was so great that their seat belts did not save the children , he says . Belgian Prime Minister : Victims include 10 Dutch people , one German and one Pole . The bus was returning to Belgium from a ski trip with 52 people aboard , most of them children .