IONIA, Mich. (WOOD) — Michigan State Police responded to a state prison in Ionia Friday afternoon after two mail room workers became ill.

Around 12:30 p.m., mail workers at Richard A. Handlon Correctional Facility on Bluewater Highway near Wall Street were reviewing packages. One that was addressed to a prisoner at the facility had a strong odor, and the employee reviewing it started to feel dizzy and nauseous, according to the Michigan Department of Corrections. Another employee who came into the mail room also had a “strong reaction” to it when they walked into the room, MDOC said.

The facility staff evacuated the mail room and called Michigan State Police. First responders arrived on scene and treated the staff who had fallen ill. MDOC said the workers “are doing fine now,” according to a release late Friday evening.

“We are happy our staff are safe and healthy and this is another reminder of the dangers our staff face everyday when criminals attempt to send drugs through the mail to prisoners,” a spokesperson for MDOC wrote in the release.

MSP is investigating, working to figure out what type of substance the mail workers came into contact with.