The blast occurred Saturday when a real-estate agent was showing the log home near Sandpoint to a couple and their son.

"They went to the house with the agent. She unlocked the door, they went in, they smelled gas, she turned the light on and at that point the house exploded," said family member Sue Peterson. "It actually blew them off the porch and into the snow."

The victims were identified as Cody Likkel; his wife, Jodi Greve; and their 6-year-old son, Mason. The name of the real-estate agent, a 51-year-old woman, was unavailable.

After the blast, the four injured people went to a neighbor's house to call for help, said Bonner County Sheriff Elaine Savage.

They were airlifted to Harborview Medical Center in Seattle for treatment. The victims suffered second- and third-degree burns, , said Capt. John Valdez of the Bonner County Sheriff's department. The burns, mostly to the hands and face, are not considered life-threatening.

The house was not leveled by the explosion and fire, but walls were damaged and all the windows were shattered.

"We're making our way through the home room by room, trying to determine what happened," Northside Fire Chief Brad Mitton told the Bonner County Daily Bee.