The over-crowded boat sank in the swollen river after colliding with a boat laden with sand at Danapur in Patna district.
The district administration, along with a National Disaster Response Force (NDRF) team, has launched rescue operations, officials said.
"All the people on the boat are feared drowned," an official said.
The threat of floods is looming large in several districts of north Bihar following incessant rains for the past several days in neighbouring Nepal.
--IANS (Posted on 25-08-2013)