At least 41 people have died after a bus in Nepal plunged off a mountainous road into a river in the eastern part of the Himalayan nation, according to reports.

Another 16 other people were injured, police officials said.

BBC reported that the bus veered off a road, lost control and dropped 400 meters (1,312 feet) from a cliff into the Sunkosi river.

Police said an unknown number of other passengers are missing after the accident in the Sindhuli district, which is located 62 miles from the principal city of Kathmandu. Officials fear that missing passengers may have been swept away by the rapidly-flowing river.

About 60 people were thought to be riding on the bus, police said.

We don't yet know whether people were travelling on the rooftop [of] this bus, Sindhuli chief district officer Beni Madhav Gyawali told BBC.

But the number of passengers certainly exceeded the number of seats.

He added: “The cause behind the accident is not yet clear. But there are reports that the bus had technical problems.”

Soldiers, police and rescue officials have reportedly faced obstacles in reaching the crash site – the bus apparently broke off into several pieces.

Local police officer Lokendra Shrestha told media that local people and more than 100 soldiers and police officers are helping with the rescue.

“The bus was overcrowded and the road was narrow,” Shrestha said.

Bus accidents are quite common in impoverished Nepal, given the poorly managed roads and overcrowded buses. Moonsoon rainfalls exacerbate the problem by triggering dangerous landslides and making roads more slippery.

Buses are especially crowded this time of year as people return to work from their home villages at the end of Dashain, the national festival that lasts a fortnight.