PHOENIX (AP) - Maricopa County sheriff's officials say they've seized 3,500 counterfeit oxycodone pills that were laced with the powerful narcotic fentanyl.

Sheriff Paul Penzone says in a statement Tuesday that a sting operation that took the pills off the street "undoubtedly saved lives."

Fentanyl is a synthetic opioid that is extremely powerful in very small quantities. Penzone noted that even small amounts can be lethal.

The narcotics were seized on Aug. 30 after members of an undercover unit arranged to buy them from 26-year-old Jesus Madueno.

Penzone's office says detectives met with Madueno, confirmed he had the drugs and arrested him without incident on narcotic sales charges.

It's unclear whether Madueno has an attorney who could comment on the allegations.