Though the children had consumed food on Monday night, they died this morning, police officials said.
The 20 other affected persons were admitted to a nearby government hospital.
The deceased have been identified as Birsa Purti (7), Sunita Purti (3) and Manika Munda (11).
A three-member team of doctors has rushed to the village to treat other villagers who fell ill after consuming the poisonous food, Additional District Medical Officer (ADMO),Sambalpur, Panchanan Nayak said.