More than two dozen people at a prison in Ohio became ill on Wednesday after being exposed to a mixture of heroin and the powerful opioid fentanyl, according to the Ohio State Highway Patrol.

Later on Wednesday, at least seven people at prisons in Pennsylvania also reported feeling ill, prompting the state's Department of Corrections to put all its prisons on lockdown.

In Ohio, 28 people were transported from Ross Correctional Institution in Chillicothe to a nearby hospital for treatment, including 23 correctional officers, four nurses and one inmate, according to police.

One additional inmate was treated at the prison but was not transported, police said. As of Wednesday evening, one staff member and one inmate remained hospitalized.

Police received a call at 9:10 a.m. ET about a substance exposure at the facility. All officers, nurses and inmates affected were responsive and transported to Adena Regional Medical Center for treatment, according to police.

Police said there had been no fatalities and there was no threat to the public.

Fentanyl is a powerful synthetic opioid that can be absorbed through the skin, eyes or mouth, and can cause an overdose even in small doses, according to the Mayo Clinic.

Narcan, a life-saving drug used to counter an overdose of Fentanyl, had been administered to several victims, according to police, and 300 doses of Narcan had been made available at Ross Correctional Institution.

The cellblock where the substance exposure happened had been cleared and all inmates and employees had been relocated to other parts of the facility.

Police said a hazardous materials decontamination team was headed to the prison to clean up the scene.

The incident remains under investigation.

In Pennsylvania, five prison staff members at State Correctional Institution in Albion became ill after being exposed to an unknown substance, according to NBC News affiliate Erie News Now. Those staff members were taken to a nearby hospital, Erie News Now reported, adding that two staff members from State Correctional Institution in Somerset had also reported feeling dazed and lethargic and were taken to a hospital.

Law enforcement believe that the employees may also have been exposed to a drug, but only one staff member so far has tested positive for K2, a potent synthetic cannabinoid.

Following these reports on Wednesday, Pennsylvania Department of Corrections Secretary John Wetzel put all the state's prisons on lockdown, citing multiple sickened staff members over the last few weeks.

"The safety and security of our employees is my number one concern," Wetzel said in a statement. "Our state prisons, especially those in the western part of the state, have experienced recent incidents in which employees have been sickened and we need to get to the bottom of this issue now."

Pennsylvania prison mailrooms will be closed and visitors will not be allowed at the locations for the duration of the lockdown, according to the release.