It happened around 2 p.m. Monday in a home at the Lake Harmony Estates development in Kidder Township, Carbon County. Neighbors say an explosion shook their homes.
Investigators believe a couple and a worker were inside the home at the time of the blast. Officials at the scene did not identify the victims but said two were hospitalized.
An excavation crew and rescue dogs were brought in to search through the rubble.
Investigators remain on the scene.