Police said the bus carrying college students and teachers drove off a highway in a mountainous area.

A bus carrying college students and teachers veered off a highway in a mountainous area of southwestern Nepal and plunged into a river, killing at least 21 people and injuring 15 others, officials said.

The bus was returning to the town of Ghorahi from an educational trip to Dang district when the accident took place on a road near Tulsipur town on Friday, police officer Prem Bahadur Shahi said.

“It plunged about 700 meters below the road. We have found the bodies of 13 men and three women so far,” he said.

Those injured in the accident were being treated at a local hospital, Shahi said, adding that at least two of them were in a critical condition.

Reuters news agency reported that the rescue operation was difficult since the crash site is situated in a remote area, around 400km west of Nepal’s capital, Kathmandu.

The students and instructors were from Krishna Sen Ichhuk Polytechnic Institute and were visiting a farm in a nearby district as part of their botany field trip.

Road accidents are common in mountainous Nepal, which in recent years has seen a drive to build roads connecting remote regions to towns and cities across the country.

Twenty people were killed last week when a mini-truck skidded off the road in Nuwakot district in central Nepal.