Police said the boat carrying 30 people to a temple at Dadomau Ghat in Saloni village capsized midway.
While the bodies of eight victims were recovered, six others are still missing.
The rest either managed to swim ashore or were rescued by fishermen and locals. The dead include four children, two women and two men.
Rescue teams, including divers, were rushed to the spot, 30 km from the district headquarters.
Thousands of people visit the Devi Mela on Dadomau Ghat, and are ferried to the site on overloaded boats.
Poor light was hampering the rescue efforts and efforts were on to bring floodlights to continue the rescue.