At least 34 people have reportedly been killed after a small bus veered off a steep road near the town of Karatu, in Tanzania's Arashu region on Saturday and plunged into a river, local media reports said.
The bus was taking children from their school in Arusha for an exam.
The deceased included 29 students.
The driver of the bus and two teachers also died in the incident.
Tanzania's President John Magufuli has expressed his condolences to families of the victims.
President Magufuli also described the accident as a "national tragedy".