The water level started rising due to Saturday's landslide that killed eight people in Nepal. Mud and rocks came crashing down and blocked a tributary of the river.
According to reports reaching here, thousands of people have fled their houses fearing the worst after government issued an alert over likely floods in Supaul, Saharsa, Madhubani, Purnea, Khagaria and Madhepura districts of the Kosi region.
"Hundreds of people have taken shelter on high-rise roads and embankments in Supaul, Saharsa and Madhepura," state Water Resources Minister Vijay Kumar Choudhary said.
The state government has evacuated nearly 20,000 people till Sunday morning.
Principal secretary for disaster management department (DMD) Vyasji (one name) said the evacuated people have been put up in relief shelters. The number of evacuees will go up by Sunday evening.
He admitted that government agencies concerned are preparing for the worst. "We are ready to face any situation after Nepal alerted the state government Saturday," Vyasji added.
"I was informed government's appeal has worked and people have moved out," Choudhary said.
Eight teams of the National Disaster Response Force and three of the State Disaster Response Force have been rushed for any emergency.