On Saturday night the authorities in Gansu said the investigation would be led by provincial leaders working alongside a task force from the State Council, the country’s cabinet.
Parents said local tests had not highlighted that anything was amiss and the problem only came to light when the children were tested in another province.
The local police said on Tuesday that the kindergarten was suspected of using inedible paint to add colour to food and had detained eight people, including the principal.
The provincial investigation team is headed by party chief Hu Changsheng and governor Ren Zhenhe, working alongside other officials, police and party discipline inspectors.
Experts from the national environmental and health ministries and a task force from the state council’s food safety commission will also be involved, the statement said.
