Fire Service spokesman Andrew Norris said firefighters from Dunedin City and Willowbank Stations were called to a fire in the wall of a student flat in Albany St at 3am yesterday.
University of Otago fifth-year medical student Gavin Lee (26), of Auckland, said he was studying in an upstairs bedroom in his Clyde St flat at 3am and smelt burning.
He initially believed the smell was coming from the nearby Cerebos Greggs factory in Forth St but he looked outside and saw "massive" flames coming from the roof cavity of a neighbour’s single-storey house below.
Mr Lee rang the Fire Service and then ran to the burning flat to find Campus Watch staff helping the residents from the flat.
At weekends, people often partied on roofs below his bedroom window but not on Saturday night, he said.
Fire Service Otago and Southland assistant area commander Rodger Smith said how the fire started was being determined.
Mr Smith confirmed a mattress had been leaning against a flat wall before the fire but he could not confirm if it was the point of origin for the blaze.
"We know the fire started on the outside of the house but that’s all we can say at this stage."
Campus Watch staff who evacuated the residents saw fire burning on an outside wall on the flat’s eastern side and in the roof.
The flat had smoke alarms but they had not triggered because the fire was burning externally and ‘‘hadn’t penetrated the internal part of the building’’.
Fire damage was restricted to the one property.
"That was down to the fact the fire was noticed very early and we were able to get there quickly and extinguish the fire."
The residents declined to comment when approached by the Otago Daily Times yesterday.
East Otago-Southland fire risk management officer Cathy Trevathan inspected the fire scene yesterday morning.
Ms Trevathan declined to comment when contacted yesterday as it was a police matter.
A police spokeswoman said the fire was being treated as suspicious and the investigation was continuing.
University of Otago acting vice-chancellor Prof Vernon Squire said the students from the flat were "fine and in good spirits".
"We have offered them support, should they need it."
University deputy proctor Andy Ferguson said "the vigilance and quick actions" of Campus Watch staff had to be commended.
In May, three students were injured after a suspicious fire at 660 Castle St.
