Firefighters rushed to a house in Arrowtown on Sunday night to find the roof ablaze.
Two crews from Frankton and Arrowtown responded within 15 minutes of the call at midnight.
Fire and Emergency New Zealand shift manager Andrew Norris said the fire was out by 12.45am, but firefighters remained until 2am to ventilate the house.
"There will be water damage for sure [to the house] and maybe some smoke damage," he said.
"Water damage can be quite catastrophic in itself, because it is normally full of ash and soot."
Mr Norris confirmed that no one was injured, but was unable to say if anybody had been in the property at the time.
A fire investigator resumed inquiries this morning, having spent several hours at the site yesterday.
