The incident occurred at The Goddard School at a Valentine's Day party Friday, the St. Louis Post-Dispatch reported.
"As soon as we learned this candy was placed in a few of our children's Valentine's boxes, we notified all parents in the classroom. To our knowledge, no child consumed the candy," said school owner Marla Brunk. "We take incidents like this very seriously. We have self-reported the incident to our corporate office and state licensor, and are working with the state to investigate the situation. As a precaution, the teachers responsible for the classroom will be on probation until the investigation has concluded."
Missouri Department of Health and Senior Services spokesman Ryan Hobart confirmed the incident was reported and said an investigation as been started.
Brunk said the school spoke with the parent who mistakenly put the chocolates in the boxes for students, adding that she was very apologetic and said she didn't know there was alcohol in the candies.
"(Investigators) are working with us to understand the situation and how this can be prevented in the future," Brunk said.