The Drug Enforcement Administration has issued a public health warning as it cracks down on a potent synthetic opioid being sold in the city.
The DEA made its first carfentanil bust in the Bronx this week, resulting in three arrests.
All three men have been charged with conspiring to distribute heroin and more than 100 grams of carfentanil.
The drug is often used as an elephant tranquilizer.
Law enforcement officials say authorities found the narcotics and production materials following an apartment search.
One of the men allegedly sold drugs to an undercover officer on three occassions.
The DEA says carfentanil is 100 times more potent than fentanyl.