One person was unaccounted for, Thornton fire crews said. The owners of the home told authorities the car and motorcycle of a third person who lived there were parked outside, the Denver Post reported.
It wasn’t immediately known what caused the explosion or whether there were any injuries.
City spokeswoman Lisa Wilson told the Post the response was in “recovery mode.”
“The scene is unstable and there are hot spots, and so the investigators have to move very slowly,” she said.
Video from television stations’ helicopters showed little of the home remained standing, and debris was spread over nearby vehicles and homes as far as a block away.
The explosion could be heard for miles. Neighbor Robert Lance Russel told KCNC-TV the blast knocked him and his son off their feet at their home across the street.
Russel said they called out to see if anyone was in the debris but heard no response.
Todd Branson, who lives behind the home that exploded, said he was watching TV when he heard a boom.
“My back window just blew in, my screen door, the glass just totally blew in. When I had a chance to go out and see my back fence, my back fence was completely gone,” he told KUSA-TV.
The explosion caused a fire amid the remains of the house, and it spread to a nearby tree. Residents with garden houses tried to douse the blaze, which fire crews had under control soon after arriving in the neighborhood about 10 miles north of Denver.
Thornton Fire Department officials did not immediately return a call for comment Thursday evening. The department’s Twitter page said technicians were shoring up the destroyed house in order to improve the search conditions.
Fire investigators were on the scene.