Law enforcement officials in Georgia have identified two new strains of the highly potent opioid fentanyl that may be immune to the opioid overdose antidote naloxone, The Atlanta Journal-Constitution reports.

The strains, called acrylfentanyl and tetrahydrofuran fentanyl, were identified by the Georgia Bureau of Investigation (GBI) in March. “It is unknown how the human body will react to both drugs since they are not intended for human or veterinary use,” GBI said in a news release. “They both can be absorbed through the skin and are considered highly dangerous.”

Acrylfentanyl was banned in Georgia in April.