The buses were on the key road connecting Nepal’s capital to southern parts of the country when they were swept away on Friday near Simaltal, about 120km west of Kathmandu.
Three people were ejected from the buses and are being treated in a nearby hospital.
The first body was recovered Sunday some 50km from where the buses fell. Other bodies were recovered from as far as the border with India.
Two of them were found in Tribeni, more than 96km from the landslide site, officials said.
Relatives of those missing gathered on the river seeking information as rescuers from the security forces used magnets, scuba diving equipment and underwater sonar imaging devices for the search.
Nepal’s rivers are generally fast-flowing due to the mountainous terrain. Heavy monsoon downpours in the past few days have swollen the waterways and turned them murky, making it even more difficult to see the wreckage.
Monsoon season brings heavy rains to Nepal from June to September, often triggering landslides in the mountainous Himalayan country.
The government imposed a ban on passenger buses travelling at night in the areas where weather warnings are posted, according to the home ministry.