New Mexico authorities said Friday that the mystery substance that sickened more than a dozen first responders in Mountainair was a deadly mix of fentanyl, methamphetamine and para-fluorofentanyl. The discovery came after firefighters and other responders were exposed at a home where four people were found unresponsive.

Two of those victims were pronounced dead at the scene. A third later died at the University of New Mexico Hospital, while a fourth survived. Officials said 25 people were exposed to the substance in all, and 20 were hospitalized for treatment before being released. Two others remained hospitalized after arriving in serious condition.

Authorities identified two of the people who died as Micah Rascon, 51, and Georgia Rascon, 49. Both the survivor and one of the deceased were given Narcan, a medication used to reverse opioid overdoses. The identification of the substance ended two days of uncertainty after first responders were rushed to the home and more than a dozen of them ended up in the hospital.

New Mexico State Police Chief Matt Broom said the incident was tied to exposure to a powdered opioid substance inside the home, and on-scene DEA laboratory analysis confirmed the presence of fentanyl, methamphetamine and para-fluorofentanyl, also called P4 fentanyl. He described para-fluorofentanyl as a more illicit form or version of fentanyl.

The response in Mountainair had the feel of a hazmat call from the start, with crews confronting an unknown substance before authorities could identify what they were dealing with. By Friday, the uncertainty was gone, but the toll was already clear: three dead, two people still in hospital and a first-responder exposure event serious enough to send 20 people for treatment. What happened in that home now stands as a stark warning about powdered opioids and the danger they pose not only to users, but to the people called to help them.