After the principal decorated the food with inedible paint, more than 200 children in northwestern China were treated for lead poisoning in the hospital.
Eight people were arrested after tests showed food samples from a kindergarten in Ganxi Province, with a lead content of 2,000 times higher than the national security limit.
A total of 233 children from Pedding kindergartens had high blood lead after eating steamed red cakes and sausage cornbread.
According to a police statement, the school principal asked kitchen staff to buy paint online.
But after the children became ill, officers had to look for hidden supplies.
The statement said the paint was clearly marked as inedible.
A parent told the BBC he was concerned about the long-term effects of lead poisoning on his son’s liver and digestive system.
Mr Liu took his child to Xi’an hospital for testing last week after other parents raised an alarm. His son now needs 10 days of treatment and medication.
Video broadcast by Chinese state media said it came from CCTV cameras in the kitchen, indicating that staff added paint pigments to their food.
Investigators found that the lead levels of red date cake and corn sausage rolls were 1052mg/kg and 1340mg/kg, respectively, both exceeding the national food safety standard limit of 0.5mg/kg.
The heads of private kindergartens and seven other (including their main investors) will now be investigated for suspected production of toxic and harmful foods.
It is not known how long the paint has been used in food, but several parents told Chinese media that their children have been complaining about stomach and leg pain and lack of appetite since March.
After raising concerns to local authorities, an investigation was conducted.
Tianshuyi Mayor Liu Lijiang said the incident exposed shortcomings and loopholes in public food safety oversight and the city will learn from the event.
