Police in northwestern China have arrested six suspects after more than 200 children were found to have high levels of lead in their blood at a privately run kindergarten, authorities said.

Seventeen officials have also been placed under disciplinary investigation, and 10 others, including senior health and education officials in Tianshui city and its Maiji district, Gansu province, face formal accountability procedures, according to a report released on Sunday.

Investigators found the lead exposure came from food prepared at the Peixin Kindergarten, not from environmental contamination. Tests of air, water and soil in the area found no lead pollution.

The arrests come after eight people were initially held for questioning earlier this month while investigations were ongoing. Among those detained were cooks, management and an investor at the kindergarten.

On Sunday, officials revealed in a report that six had been arrested on suspicion of producing toxic and harmful food.

The case came to light on July 1, when market regulators and police in Maiji district received reports of abnormal blood lead levels among children at Peixin. All 251 children enrolled were examined, and 233 were found to have elevated lead levels. At least 201 children were hospitalized for treatment.

The incident has sparked widespread concern due to the harmful effects of long-term lead exposure on children. The World Health Organization lists lead among the top 10 toxic substances of public health concern.

A joint investigation team tested 232 samples, including raw materials, cooked food and water from Peixin. Authorities found that the kindergarten's management had instructed staff to add brightly colored but inedible industrial pigments to foods such as corn rolls and jujube cakes (steamed buns), to make them look more appealing to children and parents.

Two samples from Peixin — a tricolor red date sponge cake served at breakfast and a corn roll with sausage served at dinner — failed to meet food safety standards. The samples contained lead levels of 1,052 milligrams per kilogram and 1,340 milligrams per kilogram, respectively, far above the national limit of 0.5 milligram per kilogram.

Authorities said the kindergarten was operating without a license and that local education and market supervision departments failed to carry out oversight. Some officials are suspected of accepting bribes and favors from the kindergarten's investor. Disciplinary and criminal investigations have been launched against officials, including the head of the provincial health commission and the mayor of Tianshui.

Health authorities said all affected children received treatment, with nearly all now discharged after their blood lead levels dropped by around 40 percent on average. The government is covering medical costs and has set up a monitoring program to track the children's recovery.

The Gansu provincial government issued a public apology, pledging "zero tolerance" for regulatory failures and promising to strengthen food safety and health oversight in schools across the province.

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