MOUNTAINAIR, N.M. (AP) — Three people are dead and more than a dozen first responders had to be quarantined and assessed Wednesday for possible exposure to an unidentified substance after being called to a suspected drug overdose at a rural New Mexico home, authorities said.Four people initially were found unresponsive inside the Mountainair home east of Albuquerque, New Mexico State Police said. Three died, while the forth was being treated at an Albuquerque hospital, police said. Their names weren’t released.First responders who arrived at the home were exposed to the substance and began experiencing symptoms, including nausea and dizziness, authorities…