NEW : Rural crash area had clouds and reduced visibility . NEW : `` These are difficult times , '' president says at public funeral . Investigators do n't find evidence of an explosion or a fire aboard the aircraft . Mexican Interior Minister Jose Francisco Ruiz Massieu said that there were no signs of sabotage on board the plane.
NEW : Rural crash area had clouds and reduced visibility . NEW : `` These are difficult times , '' president says at public funeral . Investigators do n't find evidence of an explosion or a fire aboard the aircraft . Mexican Interior Minister Jose Francisco Blake Mora dies with seven others .