A two-storey Gordon St house was destroyed by fire in a matter of minutes.
A male occupant was in the shower at the time the fire was believed to have started.
The man was alerted through smoke alarms as well as by his dog barking.
The occupant escaped out the back door as the fire quickly engulfed the wooden house.
Fire and Emergency New Zealand fire risk management officer Marty Jillings said usually it took just four minutes for a fire to fill a house, and considering it took the fire service about three minutes to arrive it showed how little time people had to escape safely.
He said Tuesday's fire provided another strong message to people around the importance of having working smoke alarms.
In this case Mr Jillings said the occupant's dog deserved credit as well.
''The dog will be getting a bit extra for tea tonight, I would say.''
Mr Jillings said Fire and Emergency had a good app available, called Escape My House, which showed people just how quickly their house could be engulfed by flames in a fire.
Winds delayed fire investigators yesterday morning because of concerns over the structure of the gutted house.
However Mr Jillings confirmed yesterday afternoon they had been able to carry out an investigation.
While he was not in a position to release the findings yet, he confirmed the fire was not suspicious.
The Invercargill City Council was yesterday organising the demolition of the gutted house for safety reasons.
