CHILLICOTHE, Ohio (AP) — Prison guards and nurses were among over two dozen people treated for possible drug exposure inside an Ohio prison Wednesday, the state highway patrol said.

The individuals, who included 20 guards, four nurses and one inmate, started showing symptoms of an overdose around 9 a.m. at Ross Correctional Institution, said patrol spokesman Lt. Robert Sellers.

They were administered naloxone, a drug used to combat overdoses caused by opioids such as heroin or fentanyl. The prison is about 44 miles south of Columbus. Sellers said the patrol made 300 doses of naloxone available if needed.

Contraband fentanyl, a powerful synthetic opioid, is suspected, possibly dispersed into the air by a fan, said Sellers, who emphasized investigators were still trying to determine what happened.

Inmates were evacuated from the unit where the exposure occurred, and a hazmat team from the Columbus fire department was summoned to clean up the affected area.

Also Wednesday, Pennsylvania’s state prisons were on lockdown after staff members at a fourth prison required treatment in recent weeks from exposure to a yet-unidentified substance described as a liquid synthetic drug.

It wasn’t clear whether the incidents in the two states were related.