The State Fire Marshal’s Office says a leak in a propane line caused the explosion at the L.E.A.P. building in Farmington last week.

According to Maine Department of Public Safety Spokesman Steve McCausland, investigators say they located the leak in the propane line which was buried under the paved parking lot. McCausland said the line went from an outside propane tank located at the rear of the property, under the parking lot and into the basement of the building.

Investigators conducted several tests last week on the propane line which revealed a significant leak and they continue to work on what caused that leak, McCausland said. The leaked propane permeated the ground under the parking lot and some of that gas then made its way into the basement, investigators said. Normally propane has a distinctive odor from an additive that is added to the fuel, but investigators think that odor may have been filtered by the soil under the parking lot, according to McCausland.

The propane tank had been filled Friday, Sept. 13, with nearly 400 gallons of propane but the tank was empty on Monday morning, prior to the explosion, when it was examined by maintenance supervisor Larry Lord and a second LEAP employee. The propane was used in the building as fuel for the furnace and water heater, McCausland said.

The work continues to determine how the line was damaged and what sparked the leaked propane in the building that created the explosion.

Fire marshals continue to work with the Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF), Farmington police and fire departments and the Maine Solid Fuel Board.

Investigators say Larry Lord was in the basement with Farmington firefighters “TD” Hardy, Joseph Hastings and Scott Baxter when the explosion took place. Fire Captain Michael Bell was on the first floor, Fire Chief Terry Bell was near the rear door of the building, and Deputy Fire Chief Clyde Ross and Firefighter Ted Baxter were outside the building in the parking lot, according to McCausland.