The bus carrying schoolchildren plunged off a road into a gorge in the country's north. Tanzania's president has described the crash as an "immense pain" for the whole country.
At least 35 people, including 32 children, were killed when their bus plunged into a gorge in northern Tanzania on Saturday.
Tanzanian President John Magufuli sent his condolences to the families of the victims "at this time of tragedy and grief."
In a statement he said, "This accident extinguishes the dreams of these children who were preparing to serve the nation, it is an immense pain for the families involved and for the whole nation."
The children from the Lucky Vincent Primary School in the northern city of Arusha were believed to be between 12 and 14 years old. They were travelling to take an examination at another school.
The cause of the crash was not immediately clear, but it appeared that it happened when the bus was going down a steep hill in rainy conditions, according to Arusha Regional Police Commander Charles Mkumbo, who spoke by telephone to news agency Reuters.
"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," Mkumbo said.
All of the bodies have been recovered. Photos posted on local media showed one end of the bus was crushed. Three people reportedly survived the crash, and were rushed to hospital.
Tanzanian government data shows the East African country of 53.5 million saw 3,574 people killed in traffic accidents in 2015. Poor infrastructure and maintenance are considered the primary factors behind the dismal numbers.
bik/se (AP, AFP, dpa)