Police in the city of Loudi, in China's Hunan Province, have arrested a 34-year-old woman who apparently injected rat poison and herbicide into yoghurt drinks which she handed out to young children.
Nineteen children became unwell and three are seriously ill, though doctors say none of their lives is in danger. Police believe the detained woman suffers from a mental disorder and investigations are continuing.
In May the head of a kindergarten and her accomplice were arrested in northern China after they injected rat poison into yoghurt drinks in a bid to damage the reputation of a rival school. Two children, aged five and six, died. Shi Haixia and Yang Wenming admitted poisoning the children.
In 2008, in one of the worst cases of its type recorded in China, thousands of children fell ill after consuming tainted milk powder. Six children died and two people were executed after being found guilty of supplying the powder to local schools.
In the Indian state of Bihar in October, the head of a school was arrested after 23 students died when they ate a meal cooked in mustard oil laced with insecticide. Eighty other children at the Navsrijit school also fell ill. The principal, Meena Kumari, and her husband were both charged with murder.