Three nursery school teachers have been arrested after allegedly giving a class of toddlers gummy bears containing the sleep aid melatonin to "calm them down for nap time".

Des Plaines police have charged 25-year-old Ashley Helfenbein of Chicago, 19-year-old Jessica Heyse of Des Plaines and 32-year-old Kristen Lauletta of Niles with of endangering the life or health of a child and battery after a fellow employee of the daycare raised the alarm.

Authorities were called to the Kiddie Junction Daycare Center in Des Plaines on 2 March following a "suspicious incident". Parents hadn't given permission for their children to receive the melatonin.

The three women admitted to distributing gummy bears with melatonin to 12 children aged between two and three-years-old. They claimed that they didn't think believe that giving the children the gummy bears was inappropriate because it is available over-the-counter. "This is just a horrible case of bad judgement," Des Plaines Police Chief William Kushner said.

Police notified the parents of every child at the daycare about what had transpired and only one could recall their child being groggy after being picked up. "Fortunately, no child was seriously injured that we know of at this point. It's limited to the one classroom," Kushner added.

Heyse, Helfenbein and Lauletta are expected to appear in court in Skokie, Illinois next month.