District Magistrate Saumitra Mohan says the vessel overturned Saturday night as the villagers were returning to their homes across the river despite the crew's warning that the boat was overcrowded.
Mohan said the rescue work was completed Monday, with dozens of people rescued and the 18 bodies recovered.
He said the boat became unstable and sank at a depth of 28 meters (70 feet) amid a strong current, the Associated Press reported.
Accidents are common in India as many ferries are poorly built and often overcrowded, with little regard for safety regulations.