NEW : Experts from Russia , France and Britain will help investigate . The twin-engine plane crashes soon after takeoff , carrying 12 people . The cause of the crash was not immediately known . The crash is Yaroslavl 's worst air disaster since a crash in Britain last year .
NEW : Experts from Britain , France and Canada will help investigate . The twin-engine plane crashes soon after takeoff , carrying 43 people . The cause of the crash was not immediately known . The crash is Russia 's worst air disaster since a crash in Yaroslavl last year .