Eight inmates were treated for overdoses of fentanyl at a San Diego County jail, authorities said.
The overdoses occurred Tuesday night at George F. Bailey Detention Facility in the Otay Mesa area of San Diego, the county Sheriff's Department said.
Deputies and medical staff administered Narcan, which is given to counteract opiate overdoses and were taken to hospitals and later returned to jail, authorities said.
There was no immediate indication of how the inmates obtained the drug.
The Sheriff's Department said it uses X-ray body scanners, visitor searches and drug-sniffing dogs to prevent drugs from entering county jails.
Fentanyl, a synthetic opioid, is dozens of times stronger than heroin and a tiny amount can kill.