The incident occurred at Ranauli village under Bathnaha police station limits, the police said.
A wedding was scheduled to be held in a house in the village tomorrow and the children had gone there to have morning tea.
The children, all minors, complained of nausea and started vomiting after drinking the tea, and two of them fainted, Station House Officer of Sitamarhi Town police station Anil Sharma said.
The two children, who had fainted, died when they were taken to a sorcerer for treatment, Sharma said.
The 11 other children were admitted to Sitamarhi Sadar Hospital, Civil Surgeon Bindeshwar Sharma, said, adding that all of them were out of danger.
The reason behind the death of the two minors could be ascertained after post-mortem examination, Sharma said.