Photo shows scene of a school bus accident on Saturday morning that killed at least 32 people, including 29 pupils in northern Tanzania's Karatu District. (Xinhua)

ARUSHA, Tanzania, May 6 (Xinhua) -- Tanzanian President John Magufuli has sent a message of condolence to families of 32 people including pupils, two teachers, and a bus driver who died in a school bus accident on Saturday morning.

In the message released on Saturday evening, the Tanzanian leader described the accident as "national tragedy."

The children were travelling by bus from their school in Arusha to sit for an exam on Saturday.

All were students at the Lucky Vincent Primary School in the northern Tanzania's safari capital of Arusha.

Photo shows victims of the accident rushed to nearby hospitals.(Xinhua)

Innocent Mushi, director of the school, said the dead pupils include 12 boys and 17 girls.

Several other children are severely injured and recovering from their injuries in hospital.

Earlier, Theresia Mahongo, Karatu District Commissioner, said the school bus plunged into the Marera gorge, around 150 km from Arusha city.

Photo shows victims of the accident rushed to nearby hospitals.(Xinhua)

"The accident happened when the bus was descending on a steep hill in rainy conditions and plunged into a gorge," said Charles Mkumbo, Arusha regional police commander.

"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 official added.