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.  

Investigators on Friday said they located the leak in the propane line that was buried under the paved parking lot. 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, police said.

Investigators discovered the leak after conducting several tests on the propane line.

Investigators believe the leaked propane permeated the ground under the parking lot and some of that gas then made its way into the basement. Although propane has a distinctive odor from an additive that is added to the fuel, investigators think that odor may have been filtered by the soil under the parking lot.

The propane tank had been filled Friday, September 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.

Farmington Fire Dept. Capt. Michael Bell, 68, was killed in the explosion. Bell was a 30-year member of the fire department.

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