Many people remain trapped in the flood-affected area (Pic: Tearfund)
More than 50,000 people are now reported to have fled their homes after a dam collapsed in south-eastern Nepal, officials say.
The Chief District Officer (CDO) of Sunsari district has said a major rescue operation is now under way.
So far 19,000 people have been removed from the flood-affected area, and thousands more still need to be evacuated, he said.
The rescue operation is being primarily conducted by the army and police.
The Koshi dam on the Saptakoshi river in Sunsari district collapsed on Monday afternoon after breaching embankments.
Negotiations are also taking place between Indian and Nepalese officials regarding the re-building of the dam at Biratnagar in south-east Nepal, Sunsari CDO Durga Nath Bhandari told the BBC.
It will take three weeks before transport can start functioning normally in the area, because the road which connects the south-east to the rest of the country is under water, he added.
Witnesses on the ground have described the plight of those affected by the floods as "pathetic".
Many flood victims are suffering from diseases
They say many flood victims are not getting enough to eat, with government offices and other public buildings - including schools - crammed with displaced people.
Health officials are now concerned about an outbreak of waterborne diseases - they say six people have died so far.
Many people suffering from diarrhoea and fever have been taken to the district hospital, police said.
Aid workers say many sources of electricity supply have been damaged and drinking water is scarce. They say some people have not eaten properly for three days.
About 28 million people were affected by the floods in India, Bangladesh and Nepal last year, in which more than 400 people died.