Portland police are warning the public about counterfeit pills.

Police arrested 22-year-old Justin Williams of Saco last week when they found him with enough fentanyl to kill more than 41,000 people during a traffic stop. Officers also uncovered 628 pills, which included Adderall, Xanax and Oxycodone.

Upon testing, the department says the pills were found to be counterfeit, and many of them tested presumptive positive for fentanyl and methamphetamines. Police say a 17-year-old Portland girl overdosed on fentanyl when she ingested what she believed was an Oxycodone pill.