The blaze in Harbour Tce broke out about 8pm on Saturday.
A Fire and Emergency NZ spokesperson said an investigator had since determined the fire started outside the three-storey building.
Investigations to establish the origin and cause of the fire were still under way but a police spokeswoman said it was being treated as suspicious.
‘‘Officers have spoken to a number of witnesses and would like to hear from anyone with information who has not yet spoken to us,’’ she said.
On Sunday, neighbour Te Koha Jansen said he saw a hoard of household appliances on the property ‘‘exploding and setting alight’’ during the fire.
‘‘They were popping and the gas tanks were exploding and catching,’’ he said.
Other students in the area had also noticed the whiteware, with one saying ‘‘they had like 10 trillion fridges and stuff’’.
Witnesses said the glow of the fire was visible from several blocks away and one described it as ‘‘pretty massive’’.
While it was initially feared there were people inside the property, a full search by firefighters found it was empty.
After the fire, several people contacted the Otago Daily Times to say a person was seen riding an e-scooter into the house and doing ‘‘burnouts’’ inside before people began to flee the building.
• Police 105, file number 26064/6961.
