Heavy rains lashed the catchment areas of Nepal.
Flood situation has further deteriorated following an increase in water level of a group of rivers, an official said, adding that the surging water of the rivers have inundated fresh areas.
"Flood water is spreading to new areas, forcing people to take shelter at safer places," the official said.
Authorities have ordered closure of some local educational institutions until further orders.
Reports said road link between Nepal and Sitamarhi, Madhubani and Sheohar districts of Bihar has been cut off for the past 15 days.
Flood waters have inundated parts of rail track.
The recent floods in Bihar have claimed over 100 lives and affected 800,000 people.
Floods have also ravaged northeastern state of Assam, killing 69 people and affected 2.8 million.