New Mexico authorities are investigating an incident at a Mountainair home that left three people dead and hospitalized nearly 20 first responders exposed to a still unidentified substance.

The New Mexico State Police reported that officers responded around 11:00 a.m. to support the Torrance County Sheriff's Office in what was initially reported as a possible overdose related to an unknown substance, Fox News reported.

Upon entering the home, authorities found four people unconscious. Three of them were declared dead at the scene.

First responders began to show symptoms

Authorities said 18 first responders were exposed to the substance and subsequently began experiencing symptoms such as nausea and dizziness.

The fourth occupant of the home and the affected rescuers were taken to the University of New Mexico Hospital, where they remain in quarantine and under medical observation.

Police indicated that the two first responders remain in serious condition.

Mountainair Mayor Peter Nieto reported that three of the four Mountainair EMS emergency medical technicians have already been discharged.

However, emergency chief Josh Lewis will remain hospitalized overnight to continue under medical observation.

According to Nieto, Lewis was the first lifeguard to enter the residence.

Specialized teams work to identify the substance

Hazmat teams from Albuquerque Fire Rescue are currently working to identify the substance involved in the incident.

Researchers believe the material could spread through physical contact, although they noted there is no evidence of airborne transmission.

The authorities also stated that there is no threat to the population and that a security perimeter was established around the home.

In a post posted on Facebook, Peter Nieto indicated that the exact cause of the incident is still unknown.

However, he noted that preliminary information suggests that narcotics could have been a factor related to the case.

For its part, Mountainair Public Works ruled out that the incident was linked to carbon monoxide or natural gas leaks.

The investigation continues as specialists analyze the scene and carry out tests to determine what substance caused the emergency.