Meanwhile, the parents of the deceased children have collected the bodies for cremation.
The accident took place on Thursday evening when a school bus (Ga 1 Kha 1459) from Chitwan-based Hill Bird Secondary School returning from a picnic skidded off the highaway at Thumsi in Gaindakot in Nawalparasi district.
The bus skidded off a bridge at Kharkhare in Mukundapuri VDC-6 and fell into a ravine while trying to overtake a tractor trailer at the bridge.
The accident spot is about 200 kilometers southwest of Kathmandu.

Two critically injured students were brought to Kathmandu for treatment. One of the injured has serious injury to the head.
Altogether 139 persons including students and teachers had left for a picnic at Fulbari in Butwal on Thursday morning.
SP Shahi said there were two picnic buses – one carrying boys and another girls.
More than 50 injured are undergoing treatment at various hospitals and clinics in Chitwan.
Who teaches who: parents or children?