French police were investigating Wednesday how a bag of hashish resin blocks, eaten by kids who mistook them for breakfast cereal bars, came to be left in the grounds of a school.

The students told teachers that they found the package containing the "leafy-flavored breakfast bars" hidden between a bush and the school fence during recess Friday, Le Progres newspaper reported.

One child from the school for six to 11 year olds in Tarentaize, near St. Etienne, in central France, was rushed to the hospital later that evening by his worried mother, along with a piece of the "leafy" bar.

Tests confirmed the bar that contained cannabis resin, and the boy was sent home at 11:30 p.m. local time. None of the other children who ate the bars became ill.

The mother of the boy who got sick filed a police complaint against the school for the "admission of harmful substances."

But Inspector of Schools Pierre-Michel Brunel said that the "school team responded with vigilance but could not assume that the children had eaten [cannabis]."

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