Authorities in the Denver suburb of Thornton are searching for anyone who might have been inside a house that's been leveled by an explosion.
Thornton fire crews say one person is unaccounted for after Thursday's blast. Neighbors say the boom could be heard for miles.
Helicopter footage from television news crews shows little left standing amid the smoking ruins. Debris rained down on nearby vehicles and residences.
It's not immediately clear what caused the explosion or whether there are any injuries.
Dave Nichols tells KUSA-TV that his home two blocks away shook as though there was an earthquake. He then saw a ball of smoke and fire spew into the air.
Firefighters and police officers are responding to the neighborhood about 10 miles north of Denver.