Detective Sergeant John Hedges, of Dunedin, confirmed the cause of the fire in the Stavely building, in Jetty St, which housed the Dunedin School of Ballet, The Curtain Maker, an illegally-tenanted apartment and storage, was unknown.
"It's bit of an odd one," he commented.
The category two historic building had been due to change hands two days after the March 30 fire.
POS Development Ltd, which had bought it six months earlier, still owns the building.
Lachie Chisholm, of POS Development Ltd, said the building was now being cleaned and cleared.
No plans had been made for its future, he said.
No charges have been laid over either of two suspicious fires on Saturday, March 2.
Japanese Auto Wreckers, in Birch St, was destroyed after a pile of tyres was lit outside the premises.
Another pile of tyres was destroyed at a business in King Edward St, South Dunedin.
Det Sgt Hedges appealed for anyone with information to contact police.
