Police Scotland confirmed the “single occupant of the property is currently unaccounted for” and they believe the man may have been inside the property at the time of the blaze.
The Scottish Fire and Rescue Service sent four fire appliances to an address in the Dores area near Loch Ness, south of Inverness, at about 10.30pm on Monday.
The fire was extinguished, but due to extensive structural damage making it unsafe, fire crews were unable to enter the building.
A spokesman for Police Scotland said: “The single occupant of the property is currently unaccounted for.
“However, inquiries carried out so far indicate the occupant was within at the time of the fire. Their next of kin is being updated by officers.
“A joint investigation will be carried out with the Scottish Fire and Rescue Service to establish the full circumstances.”