In addition to the children, one adult also fell ill and required a hospital stay, Itar-Tass reported Sunday. The news agency said the children attended city kindergartens and the adult was a school cook.

The Stavropol branch of the Russian Ministry for Emergencies said the children began vomiting and experiencing fevers and headaches Thursday.

The mass food poisoning was blamed on substandard food products, Itar-Tass said. An investigation was under way to track down the origin of what was described as outdated foods.

Prosecutors were considering bringing criminal charges for alleged violations of sanitary and other food regulations.