Emergency crews were called Monday night to the scene of a house explosion near Edgerton, Alta., 260 kilometres southeast of Edmonton. (Courtesy Kelly Clemmer/Star News Wainwright)Six volunteer firefighters in Edgerton, Alta., were hurt Monday night when an abandoned rural house they set on fire after a training exercise suddenly exploded.

"The house was completely engulfed in flame for approximately for 10 to 15 minutes," said Wainwright fire Chief Steve Douglas. "At that point, it exploded."

The force of the blast threw firefighters against their vehicles and left them covered in heavy debris, which scattered as far as 300 metres from the house. It also badly damaged vehicles and firefighting equipment.

One firefighter was airlifted to hospital in Edmonton while five others were taken to nearby hospitals. Their condition was unknown, but Douglas believed that all had been released from hospital, with the exception of the firefighter who was taken to Edmonton.

Firefighters stand amid the wreckage of an abandoned house that exploded after being set on fire. (Courtesy Kelly Clemmer/Star News Wainwright)Firefighters had used the vacant house before for training exercises, and it wasn't connected to any utilities or gas lines, Douglas said.

This time, the landowner asked firefighters to set the structure on fire and burn it to the ground after they completed their exercises.

"The furnace was gone, the lines were gone, the tank was gone," Douglas said. "No water, nothing to the house at all. Completely vacant of anything like that."

Douglas said he suspects a water well near the house may be to blame.

"I know of reported cases where water wells have leaked small concentrations of methane gas, natural gas … . With the fire being lit on the main floor there is a distinct possibility that there could have been an accumulation of gas in the basement after the fire had been burning for a while."

The source of the explosion was still unknown Tuesday.

Two members of the Alberta Emergency Management Agency travelled to the scene to help local officials with the investigation.

Edgerton is about 260 kilometres southeast of Edmonton.