MARSHALL — A gas leak from a damaged LP line was the cause of a house explosion in August that killed two people, state investigators said.

Marshall Fire Chief Quentin Brunsvold said Friday that an investigation by the State Fire Marshal’s Office had come to a close. In the investigation report, lead investigator Brian Petersen concluded that the explosion was sparked by a dryer in the basement of the house, and fueled by LP gas that had built up in the basement from a leak in the supply line.

The report said there had been a new septic system installed at the house the week of the explosion, and the gas leak was likely from a pipe hit during the septic work.

The Aug. 27 explosion leveled the home of Gail and Nancy Schipansky, which was located about 2 miles east of Marshall on Minnesota Highway 19. Gail Schipansky, 74, was killed in the explosion. Nancy Schipansky, 71, was airlifted to Regions Hospital in St. Paul, where she died Sept. 2.

There was no fire at the scene when the Marshall Fire Department arrived, the report said. However, the force of the blast had completely destroyed the Schipanskys’ home. Investigators said all that remained was a pile of debris in the basement. Pieces of debris, like fiberglass insulation, were blown to the southeast of the house, and could be seen a half-mile away, the report said.

On the day of the explosion, area residents reported hearing or feeling the blast miles away in Marshall.

The investigation report said the force of the explosion also damaged an outbuilding on the Schipansky property and caused damage to a neighboring house and outbuildings. Some of the damage described in the report included drywall and cabinets knocked down inside the neighbors’ house, and a hole punched through the roof of an outbuilding by a ceiling fan launched through the air from the Schipanskys’ home.

As part of the investigation, the LP supply line on the Schipansky property was excavated, and a leak was found in a repaired section of the piping, the report said. The investigation report said a new septic system for the Schipansky’s home had been installed the week of the explosion. In the conclusion of the report, Petersen said the failure of the LP piping system was “most likely” because of pipe that was hit during work on the septic system.