One child allegedly died from being administered polio drops in Bihar's Vaishali district on Saturday.
Six other children have fallen sick after attending the polio vaccination program in Shahpur village, about 25 kilometers from Patna.
"Some children fell ill after being administered polio vaccine and one died Saturday morning," Mukesh Singh, a relative of one of the six children, told IANS.
The children started vomiting, and suffered from fever and diarrhoea after taking the polio drops.
Officials have ordered a probe into the incident.
"I have asked the concerned officials to ascertain whether incident is connected to the polio vaccine or not," Vaishal' civil surgeon Ramashish Kumar told IANS.
India was declared polio-free last year, while Bihar has remained polio-free for four years.