Kathmandu, Nepal — A landslide swept two passenger buses carrying more than 50 people into a swollen river in central Nepal early Friday. Continuous rain and more landslides were making rescue efforts difficult.

Three survivors apparently swam to safety, but by late morning rescuers had not found any trace of the buses, which likely were submerged and swept downstream in the Trishuli River. Nepal’s rivers generally are fast-flowing due to the mountainous terrain. Heavy monsoon downpours in the past few days have swollen the waterways and turned their waters murky brown, making it even more difficult to see the wreckage.

Home Minister Rabi Lamichhane told parliament that 51 passengers were missing and that more than 500 rescue personnel had been assigned to the search operation.

Elsewhere in the country, 17 people died and three more were injured due to landslides in different districts over the past 24 hours, he said.

The buses were on a key highway that connects Nepal’s capital to southern parts of the country when they were swept away at around 3 a.m. near Simaltal, about 75 miles west of Kathmandu.

More landslides blocked routes to the area in several places, government administrator Khima Nanada Bhusal said. Additional rescuers and security forces were sent to help with the rescue efforts. Police and army personnel were searching using rubber rafts. Divers with scuba gear were also dispatched, according the Chitwan district police.

The three survivors were being treated in the hospital, Bhusal said, adding that they reportedly jumped out of the bus and swam to the banks, where locals found them and took them to a nearby hospital.

A third bus was hit by another landslide on Friday morning a short distance away on the same highway. Bhusal said the driver was killed but it was not clear if there were any other casualties.

Nepal’s Prime Minister Pushpa Kamal Dahal said he was saddened by the news and expressed concern over recent flooding and landslides. He added that several government agencies were searching for the missing, in a post on the social media platform X.

On Thursday night, a landslide buried a hut and killed a family of seven near the resort town of Pokhara. The family were asleep when the landslide crushed their hut and damaged three more houses nearby.

Monsoon season brings heavy rains to Nepal from June to September, often triggering landslides in the mountainous Himalayan country.

The government has imposed a ban on passengers buses travelling at night in the areas where weather warnings have been issued, according to the Home Ministry.