More than 200 children are being treated in hospital for lead poisoning in north-west China after school cooks used non-edible paint to decorate their food.

Eight people were arrested after tests showed food samples from Peixin Kindergarten in Tianshui City, Gansu province, contained lead levels 2,000 times above the national safety limit.

A total of 233 children from the kindergarten had high blood lead levels after eating steamed red date cake and sausage corn buns.

According to a police statement, the school principal instructed kitchen staff to buy the paint online. When the children fell ill, authorities had to search for the hidden paint, which was clearly labeled as non-edible.

One parent expressed concern about the long-term effects of lead poisoning on his son’s liver and digestive system. Mr. Liu took his child for testing last week after other parents raised alarms, and his son now requires 10 days of treatment and medication.

Chinese state media showed video from the kitchen where staff were seen putting paint pigment on the food. Tests found that the red date cake and corn sausage rolls had very high lead levels—1052mg/kg and 1340mg/kg—much higher than the safe limit of 0.5mg/kg.

The kindergarten’s principal and seven others, including the main investor, are being investigated on suspicion of producing toxic and harmful food.

It is unclear how long the paint was used, but several parents reported their children had stomach and leg pain and loss of appetite since March.

The investigation began after parents reported their concerns to local authorities.

Tianshui Mayor Liu Lijiang said the incident revealed gaps in public food safety oversight, and the city will learn from this event.