MILLERSVILLE, Md. (AP) — Authorities say the synthetic opioid carfentanil has been responsible for at least six deaths in a Maryland county over a six-week period.

The Capital Gazette reports Anne Arundel County police say that six men between the ages of 19 and 54 died between April 1 and May 14 from overdoses on drugs the Office of the Chief Medical Examiner determined to include carfentanil.

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The Drug Enforcement Administration considers the opioid to be 10,000 times more potent than morphine. Carfetanil is commonly used as a tranquilizer for large animals.

County health department directors Fran Phillips says it’s possible carfentanil could have played a role in more deaths, as 25 fatal overdoses are awaiting review.

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Police spokesman Lt. Ryan Frashure says no arrests have been made in connection with the drug.

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