Kiev, Ukraine ? Nearly 360 schoolchildren in western Ukraine were hospitalized with food poisoning traced to a popular drink made of fermented milk, an emergency official said Saturday.

The first 299 children, aged between 2 and 6, became ill Friday, possibly from food prepared at seven kindergartens in the Khmelnitsky region. An additional 60 were hospitalized on Saturday, he said. Four of the children were in critical condition.

Health Ministry official Tetiana Yurchenko said a preliminary investigation showed that the source of infection as a dysentery bacteria in kefir, the drink made of fermented milk.

The Defense Ministry sent in military medics and set up 60 beds in two military hospitals to help treat the children.