As many as 66 people are believed to be missing in Nepal after two passengers buses were swept by a landslide off the highway and into a swollen river on Friday, official said.

Rescuers were trying to locate the bus and and help with rescue the passengers but the continuous rain was making rescue efforts difficult, reports AP.

The route leading to the accident area was also blocked in several places by landslides, said government administrator Khima Nanada Bhusal.

The buses were swept away around 3 am on Friday. Additional rescuers and security forces have been sent to the area to help with rescue efforts.

One bus had 24 people while the other had 42 but more could have boarded the bus while on the route, Bhusal said.

Monsoon season that begins in June and ends in September bring heavy rainfall to Nepal usually triggering landslides in the Himalayan country that is mostly covered by mountains