The woman was arrested Friday in Hunan Province after 19 students became ill and had to be hospitalized, police in Loudi City said.
The 34-year-old suspect confessed to injecting herbicide and rat poison into the yogurt drinks, which she handed out to the kids as they walked home after classes on Wednesday, police told China's Xinhua news agency.
Three of the children were in serious condition Friday, but doctors told Xinhua they and the other students would survive.
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