The landslide has blocked the Sunkoshi river, east of the capital Kathmandu, forcing thousands of people to evacuate their homes and move to higher ground.
Officials said army technicians were trying to unblock the river and allow the water to run off.
There are fears that the death toll will rise, as rescue work continues in the district of Sindhupalchowk.
Sindhupalchowk is 120 km (75 miles) east of Kathmandu.
"Police and army officials are trying to find the missing people and evacuate the villages on the riverside" a police official told AFP.
Officials said dozens of people were still missing.
The Arniko highway to Tibet has been closed and the area declared a "flood crisis zone" by the government.
Landslides are common during the June-September monsoon season in Nepal. Dozens of people die every year from flooding and landslides.
A massive landslide has buried dozens of homes in Nepal, with eight people confirmed dead and many missing.