The Ontario Fire Marshal's office is investigating a destructive fire that reduced a $7 million home under construction to rubble in The Town of the Blue Mountains.

Flames broke out in the early morning hours on Monday, and by Tuesday afternoon, the ruins of the waterfront mansion were still smouldering.

At this point, investigators said they aren't jumping to any conclusions about possible foul play.

"Our determinations are made on evidence, not conjectures, so until there is some factual, analytical components to evaluate, that's what goes into the determination, not anything circumstantial," said OFM investigator Mike Ross.

The local fire department will assist in the investigation, along with an engineer who was involved in the construction project of the newly sold five-bedroom, five-bathroom property.

Investigators will use specialized heavy equipment to dissect what's left.