At least 29 children and three adults died when a school bus plunged into a roadside ravine in northern Tanzania, authorities said.On Saturday, the bus with 40 people on board went off the road for unknown reasons near Karatu, a town about 150 km from the northern city of Arusha, Efe news reported.Police said rescue workers were working at the scene to recover the bodies.Innocent Mushi, the principal of the Lucky Vincent elementary school where the children were studying, said 17 girls and 12 boys were among the victims.Two teachers who were accompanying the minors on the trip to Karatu for some school exams and the bus driver also were killed.Tanzanian President John Magufuli lamented the tragedy and sent his condolences to the families.Traffic accidents are frequent in Tanzania and many other African countries due to the poor condition of vehicles and roads.