A fire tore through more than 25ha of forestry and scrub on Signal Hill on December 27.
The fire, which led to the evacuation of three homes in Ravensbourne, cost more than $100,000 to fight.
Detective Senior Sergeant Rob Hanna said police had not confirmed how the fire was started, whether deliberate or accidental, but understood it was "not a natural cause".
The investigation remained open and police were still speaking to people in relation to the blaze.
East Otago area fire commander Laurence Voight put out a call in the Otago Daily Times last month for information from the public that could lead to the discovery of the fire’s cause.
A person called the Fire Service with information, which was given to police, he said.
East Otago fire risk management officer Mark Bredenbeck said the Fire Service passed on names to police but did not know how the information was used in the police investigation.
On Thursday, Det Snr Sgt Hanna said the police had no suspects.
Mr Bredenbeck said a fire investigator could not determine the cause of the fire but it was "most likely to be suspicious" because of the area of the origin.
Police wanted to hear from anyone who saw unusual activity on the day of the fire or had information on the incident.
● Dunedin police (03) 471-4800, Crimestoppers 0800 555-111.
