KUNMING -- Ninety-one kids were hospitalized following a lunch at a private kindergarten in southwest China's Yunnan Province, said local government on Tuesday.

The children began to show stomachache symptoms and vomiting after they had their lunch in the New Century kindergarten in Wenshan City on Monday, said the city's publicity authorities.

They were immediately sent to the People's Hospital of the city for treatment. All of them were in stable condition.

As of Tuesday afternoon, 31 of them have been discharged from hospital.

The kindergarten has about 400 children.

Authorities are still investigating the cause.