A man who had been living in the house in Rye was being sought as a person of interest, KRDO-TV reported. Harry Mapps, 59, was in the town of about 200 people in south-central Colorado until recently, Don Leach, an investigative captain with the Pueblo County sheriff, said.
"He's not here anymore," Leach said. "We don't have any details as to why. We believe he was here recently, so he could have relevant information."
The fire was reported Wednesday morning and burned so fiercely the roof collapsed. When firefighters were able to enter the structure Thursday, they found the fire had started in two places, suggesting arson.
The bodies of two women and a man were found in the structure. Autopsies were scheduled for Friday.
Lisa Shorter, a spokeswoman for the Pueblo County sheriff, said ammunition stored in the basement fueled the fire, The Denver Post said. Leach said wood-burning stoves used to heat the building provided additional fuel.