Nine people were injured, one critically, when a natural gas explosion leveled a Denver apartment house.

Iran Press/America : First responders rescued two victims trapped inside the building, described as a “fourplex,” in Denver’s historic Baker neighborhood, said Denver Fire Captain Greg Pixley,Reuters reported.

No one else was believed trapped in the rubble, alive or dead, Pixley said, but firefighters were conducting a thorough search to make sure.

Two people hurt in the explosion were transported to Denver Health Medical Center, said hospital spokesman Simon Crittle. One had severe traumatic injuries while the other’s injuries were not as severe, he said.

Seven other people who suffered minor injuries were treated at the scene, the Denver Fire Department said on Twitter.

A man who lives in the area told Denver television station FOX31 he smelled gas as he was walking to the store, before an explosion sent bricks flying into the street.

The fire department posted pictures of the apartment building on Twitter showing its roof collapsed in the explosion, which propelled wooden beams and other rubble cascading across the sidewalk.