Hong Kong (CNN) A kindergarten teacher in China's Henan province has been detained after she allegedly poisoned 23 children by putting nitrite into their food.

The victims, who were all students at Mengmeng kindergarten in Jiaozuo city, fell ill after eating porridge supplied by the school on Wednesday morning, according to a statement posted to social media Monday by local authorities.

One child is still being treated, while another seven are still in hospital, authorities said. The other 15 children have already been discharged.

The children's sudden mass illness sparked a police investigation which alleged that the teacher, referred to only by the surname Wang, put nitrite into the porridge.

According to the US Centers for Disease Control and Prevention, nitrite is likely a carcinogen used in fertilizers, food preservation and even munitions and explosives.

Read More