Three people died and 18 first responders were hospitalized Wednesday after exposure to an unknown substance during a response to a suspected drug overdose in Mountainair, New Mexico.

Authorities were called to a home in the rural community east of Albuquerque where four people were found unresponsive. Three of the individuals have died, while the fourth is receiving treatment at a hospital in Albuquerque, according to New Mexico State Police.

During the emergency response, 18 first responders were exposed to the unidentified substance and began experiencing symptoms including nausea and dizziness. All affected personnel were transported to the University of New Mexico Hospital, where they were quarantined and are being monitored. Two of the first responders were listed in serious condition, said Officer Wilson Silver with New Mexico State Police.

Albuquerque Fire Rescue Hazmat teams are working at the scene to identify the substance involved in the incident. Investigators believe the substance may be transmitted through contact but do not believe it to be airborne, Silver stated.

Mountainair town officials have established a secure perimeter around the home and emphasized there is no threat to the public. The investigation into the nature of the substance and the circumstances surrounding the deaths is ongoing.