FORT WAYNE, Ind. (AP) — Authorities say 30 guards and a nurse at a northeastern Indiana jail have gone to hospitals for medical evaluation after being exposed to an undetermined opioid substance.

Allen County Sheriff's Department spokesman Capt. Steve Stone says all of the guards had entered one particular cellblock of the county jail in Fort Wayne after being alerted that inmates there were smoking something. He says they reported smelling smoke and feeling strange. They later were released from treatment.

Stone says a piece of paper infused with an unknown substance tested positive for opioids.

He says inmates were examined by nurses and medics, and the cell block was decontaminated.

No charges have been filed.