The impoverished woman Parvati of Chandchaur village allegedly sold off her son to Bini Devi yesterday in Devi's village Chiranjivipur in Begusarai district, they said.
The residents of Chiranjivipur village came to know about the boy and informed the local police who intimated their counterparts at Ujiarpur police station where a complaint was lodged, they said.
During investigation it was found that Parvati had sold off her son to return Rs 15,000 that she had taken from a person, they said.
A police team from Ujiarpur police station later recovered the boy from the woman who had bought him and handed him over to his biological mother, they said.
Samastipur District Magistrate Kundan Kumar said he had heard about the incident, but was yet to receive a written complaint in this regard.
The district administration has not received any request from the woman for financial assistance, he said.