Authorities say 3 people are dead and 19 more were rushed to the hospital after coming into contact with an unknown substance in Mountainair, New Mexico, on Wednesday.

According to reports, 18 of those sent to the hospital included first responders. Authorities were called to a house after reports of an overdose. They arrived to find three of four house occupants dead.

All those who were brought in are being “closely monitored,” according to police. The first responders reportedly began experiencing dizziness and nausea. Two of the first responders were listed in critical condition.

A statement added, “There is currently no threat to the public. A secure perimeter has been established, and the affected area remains limited to the residence. The New Mexico State Police are leading this ongoing and active investigation. Additional information will be released as it becomes available.”

Most of those were first responders who were showing no symptoms and were later discharged.

“At this time, investigators believe the substance may be transmitted through contact and do not believe it to be airborne,” said Officer Wilson Silver.

Mountainair Mayor Peter Nieto said in a social media post that drugs were a factor in the home. “The reality is that addiction and substance abuse are issues affecting communities all across our state and nation,” Nieto said. “There is no simple or immediate solution. Lasting change requires family support, accountability, education, and most importantly, individuals who are willing to accept help.”

Medical teams continued to monitor three symptomatic patients Wednesday evening, according to the hospital.

Mountainair EMS Chief Josh Lewis, who was the first to enter the residence, was hospitalized overnight for observation, Mountainair Mayor Peter Nieto said in a social media post.

Also among those experiencing symptoms were EMTs from Torrance County and nurses from the University of New Mexico hospital who came into contact with individuals on scene, he said. The mayor added that public works crew had confirmed that the health issues were not related to carbon monoxide or natural gas exposure.

Albuquerque Fire Rescue Hazmat teams were assisting at the scene in Mountainair, a rural community east of Albuquerque, in efforts to identify the substance involved.