At least 20 members of a marriage party were feared killed when a bus carrying 35 people fell into the Bagmati river at Kataunjha in Bihar's Sitamarhi district late on Monday night, official sources said.
The bus, on its way to Sitamarhi from Muzaffarpur, plunged into the river after the driver lost control of the vehicle while trying to save a motorcyclist, they said.
Four bodies have been fished out so far, officials said.
District Magistrate A B Prasad is supervising the rescue operation.