A Chinese kindergarten teacher has been detained after she allegedly served poisoned porridge to 23 children. The victims—who were all students at Mengmeng kindergarten in the eastern city of Jiaozuo—began vomiting and fainting after eating their breakfast at the kindergarten last Wednesday. CNN reports that one child is still being treated and while seven others are still hospitalized—15 children have already been discharged. A police investigation has alleged that a teacher, who’s only been identified by her surname Wang, put nitrite into the porridge. Police haven’t revealed any motive for the suspected poisoning, but Chinese media reported the teacher had wanted to take revenge on a colleague.