A natural gas leak — not foul play — almost certainly caused the explosion that ripped through the community of Vankleek Hill on Monday, Ontario fire officials say.

The explosion on Oct. 2 completely levelled one home and seriously damaged three others in the Champlain Township community about 80 kilometres east of Ottawa.

Pierre Yelle, a spokesperson for the Office of the Ontario Fire Marshal, said leaked gas likely found its way near an ignition source, triggering the explosion.

"And at this point it would appear that the pilot light on the hot water tank might be the … source of ignition," Yelle said.

Investigators with Enbridge, the company that distributes natural gas to homes in the area, have been working with the Fire Marshal's Office to trace the source of the apparent leak.

The explosion blasted to pieces a house on Fournier Street on the morning of Oct. 2, shattering the windows and blowing off the doors of neighbouring houses.

No one was seriously hurt, but about 200 people were later evacuated from 75 homes in the neighbourhood.

About half those residents were allowed back home Tuesday.

Fire investigators had suspected a natural gas leak as the cause.