A Middle Tennessee daycare has been shut down and four people arrested after an investigation determined that caretakers were giving children melatonin to sleep without parents’ permision.

Stewart County Sheriff Frankie Gray revealed the charges against MiMi’s Child Care employees on Thursday after parents lodged a complaint on March 25 that their children were lethargic or having other issues after staying there, according to WKRN.

Melatonin is a natural hormone involved in regulating the sleep-wake cycle. It is also used a dietary supplement in the treatment of sleep disorders such as insomnia. Detective Dana Saltkill told WKRN that investigators believe the employees had been giving children — including infants — melatonin for as long as three years.

“You know daycare, you’d think taking their child there would be somewhat safe, would be safe. After finding this out you kind of look back at it and say hmm … there’s a lot of red flags that parents didn’t pick up on,” Saltkill said. “As soon as we started investigating, we knew what to look for, so we got into it.”

Detective Lee Miller said that investigators believe at least 27 children were given melatonin.

Deputies executed a search warrant on April 28 and a week later arrested Jaime Clark, 45; Kristin Clark, 22; Jordan Darnell, 22; and Ethan Pulley, 21.

Jaime and Kristin Clark and Jordan Darnell were charged with child abuse/neglect, contributing to the delinquency of a minor, tampering with evidence, and other criminal violations. Pulley was charged with fabricating/tampering with evidence.

The Tennessee Department of Human Services said that MiMi’s Child Care surrendered its license on May 2 and is now closed.

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[Featured image: L-R, Jaime Clark, Kristin Clark, Jordan Darnell, and Ethan Pulley/Stewart County Sheriff’s Office]