BARRIE, ONT. -- A blackened skeleton is all that remains of a palatial waterfront home in the Blue Mountains following a raging overnight fire.

A neighbour of the home on Lake Drive spotted flames just before 3 a.m. Monday.

"By the time we got there, the flames were already through the roof, and it was not very long after that the thing was just completely enveloped," Mike Hutchings said.

Blue Mountains Fire Chief Steve Conn said flames were coming from all directions. At the height of the battle, there were 27 firefighters at the scene.

Conn said no one was home at the time and that the five-bedroom, five-bathroom mansion was under construction. It recently sold for $7-million in a deal expected to close in May.

An excavator will tear down the rubble that remains.

The Ontario Marshal is probing the cause of the fire. Investigators have not determined whether or not there's anything suspicious about its origins.