CINCINNATI (AP) — Officials say the substance that led to nearly 30 people at an Ohio prison being treated for drug exposure or suspected exposure was a heroin and fentanyl mixture.

Prison staff and inmates at Ross Correctional Institution in Chillicothe were treated Wednesday with an anti-overdose drug after an inmate showed drug overdose signs and some people experienced symptoms consistent with fentanyl exposure. The State Highway Patrol says an inmate and staff member remained hospitalized. Officials declined further comment Thursday.

Pennsylvania State Police declined Thursday to discuss their investigation into a substance sickening staff at Pennsylvania prisons that were locked down Wednesday. Authorities describe the substance as a liquid synthetic drug in some cases that’s absorbed through the skin.

Visits to Maryland prisons were temporarily suspended as a precaution.