KATHMANDU, Nepal (AP) — As many as 66 people were believed missing in Nepal after two buses were swept by a landslide off the highway and into a swollen river early Friday, officials said. Rescuers were trying to locate the buses but the continuous rain was making rescue efforts difficult.

Landslides also blocked the route leading to the area in several places, government administrator Khima Nanada Bhusal said. Additional rescuers and security forces have been sent to the area to help with rescue efforts.

The buses were swept off the highway around 3 a.m. near Simaltal, about 120 kilometers (75 miles) west of the capital, Kathmandu.

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

In a nearby location on the same highway, a bus was knocked by a landslide, killing the driver. It was not clear if there were any other casualties, he said.

Monsoon season that begins in June and ends in September brings heavy rainfall to Nepal, often triggering landslides in the Himalayan country that is mostly covered by mountains.