A landslide plunged two passenger buses, carrying at least 66 people, into a swollen river early Friday in central Nepal.
Continuous rain and additional landslides complicated rescue efforts.
Although three survivors managed to swim to safety, rescuers had not located the submerged buses in the Trishuli River by late morning.
Nepal's mountainous terrain contributes to fast-flowing rivers, exacerbated by heavy monsoon rains in recent days. The murky, brown waters further hindered visibility, making the wreckage difficult to spot.
The buses were on the key highway connecting the capital to southern parts of Nepal when they were swept away around 3 a.m. local time near Simaltal, about 120 kilometers (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 to the Chitwan district police.
One bus was carrying at least 24 people, while the other had at least 42, but more could have boarded en route, Bhusal said.
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 was 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.
