PLUM, Pa. — One person is dead, another critically injured and several people are unaccounted for following a house explosion in western Pennsylvania that destroyed three structures and damaged at least a dozen others, authorities said.

Allegheny County officials said three people were taken to hospitals after the blast that happened shortly before 10:30 a.m. Saturday in the borough of Plum. Officials later said one was critically injured and two others were listed as stable. More than 20 firefighters were evaluated, many for heat exhaustion.

County spokesperson Amie Downs said emergency responders reported people trapped under debris after one house exploded and two others were engulfed in flames. Crews from at least 18 fire departments were working to douse the flames with the help of water tankers from Allegheny and Westmoreland counties.

Officials told reporters at the scene that they don’t know exactly who was home and who may have had visitors at the time of the explosion, so they can’t give an exact number of people unaccounted for. The name of the person killed will be released by the county medical examiner’s office.

The cause of the explosion is under investigation. Plum and county law enforcement, as well as the county fire marshal’s office, are investigating, and the state public utilities commission and local utilities were also at the scene.

George Emanuele, who lives three houses down from the home that exploded, told the Tribune-Review that he and a neighbor went to the home before the fire got out of control, where they found a man laying in the backyard and dragged him away from the scene.

Rafal Kolankowski, who lives a few houses down, told the Pittsburgh Post-Gazette that the explosion broke the windows in his house and knocked him and his wife to the ground. After recovering and checking on his son, he went outside where he said a woman told him another woman had been upstairs and a man was in the basement. The other woman later emerged covered in white ash, but the individual in the basement had not yet exited, he said.

“It’s just tragic, I mean, it looks like a war zone – it looks like a bomb hit our neighborhood and it’s just unfortunate,” Kolankowski said. “I was just with some of the neighbors yesterday, right, and now this happens.”

Jeremy Rogers, who lives two doors down, told the paper he had been out shopping when he got an alert about a problem at his house and saw “all sorts of stuff flying around.” His family was able to get out safely, and he was allowed to go in quickly to rescue his dog. However, he wasn’t able to get the family’s three cats and hopes they are all right.