Emergency teams in Nepal on Tuesday used mechanical diggers to search through a village inundated by mud in a flash flood three days ago that left 23 people dead and more than 40 missing.

The village of Kharapani, which had a population about 100, was devastated when the Seti River burst its banks, smashed through buildings and swamped families enjoying picnics.

Witnesses described how the river suddenly swelled up on Saturday after water erupted from behind a landslide that had blocked its course upstream.

A road connecting the village to nearby settlements was destroyed and piles of rock and debris hampered relief workers trying to access the area where many of the missing are believed to be buried.

A bus is thought to have been covered by the surge of mud.

Police superintendent Shailesh Thapa said 23 corpses had been recovered and more than 40 people, including three Ukrainians, were still missing after the flood near the city of Pokhara, a popular tourist hub.

"We have mobilised four excavators to find the dead bodies that are likely to be buried beneath the debris," Thapa said.

"We searched the riverside and the entire length of the river, but we could not find the missing people. Therefore, we decided to focus on the village where a bus is believed to have been buried."

More than 150 security personnel have been involved in the search and rescue operation.

Khem Sapkota, a local official of the Nepal Red Cross Society, said he feared casual labourers who carried sand from the river bed to trucks had not been included among those who were officially missing.