Mystery ‘substance’ leaves three dead, dozens hospitalised The NightlyThree dead, 18 first responders quarantined after exposure to unknown substance at New Mexico home Fox NewsNMSP: 3 dead, 25 exposed to ‘unknown substance’ at Mountainair home KOB.comState police: 3 dead, 18 first responders hospitalized in Mountainair substance exposure Santa Fe New Mexican3 dead in New Mexico and first responders decontaminated after exposure to unknown substance ABC News – Breaking News, Latest News and Videos