BALTIMORE (AP) — A fire department investigation concludes that a natural gas explosion caused a fire that heavily damaged an east Baltimore rowhouse and caused a wall to collapse onto the street, killing a boy who was walking by.

The report on the Feb. 19 fire, released Thursday, says the explosion originated in the basement and was caused by natural gas coming in contact with an ignition source. The house had utility service and had a natural gas range and gas-fired furnace and water heater.

The investigator said the heating system or the water heater, which had a pilot light, could have ignited the natural gas.

The body of 8-year-old Troy Douglas was found crushed underneath a collapses wall of the house. Fire officials had said he was probably walking home from school.