A panel of experts said yesterday the illness could be related to yogurt served at the Lantai Kindergarten in Lanzhou, the provincial capital.

Kindergarten teachers reported children aged 3 to 5 years complaining of stomach problems, diarrhea, vomiting and fever at about 4 pm Friday, said a statement from the Lanzhou city emergency response office.

None of the children were seriously ill after medical treatment and observation, it said.

Forty of the 87 hospitalized children were discharged from hospital at noon on Saturday.

Yuan Zhanting, Mayor of Lanzhou, ordered medical staff to provide the best possible care for the children and instructed food safety authorities to step up monitoring.

Local disease control and prevention authorities are investigating the incident.