PASADENA, Md. (AP) — Officials say a fourth overdose death in Maryland has been linked to the synthetic drug carfentanil.

Media outlets report that it is the third such death in Anne Arundel County in recent weeks and the fourth in the state. Frederick County also reported an overdose death attributed to carfentanil this year.

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Anne Arundel County police spokesman Lt. Ryan Frashure says that an autopsy found that the April death of a 51-year-old man in Pasadena was due to an overdose of the drug. Carfentanil, a sedative for large animals, is considered by to be 100 times deadlier than fentanyl, which is 50 times deadlier than heroin.

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County Police Chief Timothy Altomare says police have made it their “top priority to figure out who’s selling that poison.”

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