Three people died and 18 first responders were sickened by exposure to fentanyl in a rural New Mexico home this week, New Mexico state police said.

Police initially found four people unconscious at the home in Mountainair, 90 miles (145km) east of Albuquerque. Two were declared dead at the scene and a third died at a hospital.

During the response, authorities said, first responders were exposed to the substance and began experiencing symptoms including nausea and dizziness. Eighteen were hospitalized and then decontaminated.

Preliminary findings suggest multiple powdered opioids contributed to the deaths of three residents, including fentanyl and para-fluorofentanyl (also known as P4 fentanyl), and methamphetamine.

Officials identified the deceased as 51-year-old Mika Rascon and 49-year-old Georgia Rascon. The identity of the third person has not been released by the medical examiner.

All Mountainair EMS staff were later sent home, with just the fourth person found inside the home and one first responder remaining hospitalized.

Steve McLaughlin, chief medical officer at the University of New Mexico hospital, said fentanyl appeared to be primarily responsible.

“Fentanyl is particularly dangerous because it requires only a tiny amount to cause an overdose. The tiniest possible dose of fentanyl can cause serious symptoms in an exposed individual,” McLaughlin told the Albuquerque Journal.

A New Mexico state police spokesperson said preliminary evidence did not indicate that “true manufacturing” of drugs was taking place at the home. No one has been charged in the case, authorities said.

The Mountainair police department said it had received reports that a person had not arrived at work that morning. Another employee visited the home and found four people who appeared to be overdosing.

Emergency workers entered the home with protective gear but had been advised to exercise caution, believing the cause could be a gas leak.

“This tragedy also highlights the dangers associated with illicit narcotics, especially fentanyl, and the horrible impact it has caused in communities across our state,” the New Mexico state police chief, Matt Broom, said during a news conference.

“We, as a community, must do anything and everything to address this epidemic. We owe it to our fellow New Mexicans.”

Fear of accidental exposure to the synthetic narcotic has driven police departments to spend heavily from opioid settlement funds on specialized equipment to help protect first responders from fentanyl exposure risks.

But studies suggest that there is almost no evidence that law enforcement personnel are at risk from overdoses due to accidentally touching or inhaling the drug.

Florida has passed a law to make it a second-degree felony to cause an overdose or bodily injury to a first responder through second-hand fentanyl exposure, and similar legislation has been considered by Tennessee and West Virginia, according to NPR.

New Mexico is considered a major drug trans-shipment state for dispersing fentanyl to major markets across the US.