32 schoolchildren, believed to be aged between 12 and 13, were killed in the crash in the northern region of Arusha.
Thirty-two schoolchildren, two teachers, and a minibus driver were killed in Tanzania when their vehicle plunged into a roadside ravine in the northern tourist region of Arusha on Saturday, a senior police official said.
"The accident happened when the bus was descending on a steep hill in rainy conditions," Arusha regional police commander Charles Mkumbo told by telephone.
"We are still investigating the incident to determine if it was caused by a mechanical defect or human error on the part of the driver."
The students killed in the accident, which occurred at about 9:30am in Karatu district, were from the Lucky Vincent primary school and believed to be aged between 12 and 13. They were on their way to visit another school, Mkumbo said.
President John Magufuli described the accident as a "national tragedy" in a statement.
While buses remain the main form of public transport in Tanzania, East Africa's second largest economy has a poor road safety network.
More than 11,000 people were killed in road accidents in Tanzania between 2014 and 2016, according to government data.