Something killed several residents in a rural New Mexico town, and officials are still trying to figure out what it is. On Wednesday, New Mexico State Police reported the deaths of three people at a home in Mountainair that contained an unknown substance. Several first responders potentially exposed to the substance became ill, while more than a dozen people had to be briefly quarantined. Authorities have not yet identified the substance, though it may be drug-related, and they’re not concerned about any harm to the public. “At this time, investigators believe the substance may be transmitted through contact and do not believe it to be airborne,” said Officer Wilson Silver, the Associated Press reported Wednesday. Mystery ailment According to officials, first responders were called to the house due to a suspected drug overdose on May 20. They initially found four people unresponsive inside the house, three of whom were later declared dead. The fourth person is currently being treated at the University of New Mexico Hospital (UNMH) in Albuquerque, which is about 65 miles (104 kilometers) northwest from Mountainair.

Several responders exposed to the substance reported symptoms like nausea, vomiting, coughing, and dizziness. All told, at least 18 first responders were quarantined and assessed at the same Albuquerque hospital, though most were later discharged after showing no illness. However, Mountainair EMS Chief Josh Lewis remained hospitalized overnight, according to Mountainair Mayor Peter Nieto. KOAT 7 reported Wednesday that several nurses at UNMH also came into contact with the substance and have experienced symptoms.