Fire and Emergency New Zealand specialist fire investigator Scott Cameron said the fire was a result of faulty equipment on site.
"At this stage it will be recorded as an accidental fire," Mr Cameron said.
"It’s as a result of an electrical event."
He could not say more about the nature of the electrical issue at this stage, but the matter was now being dealt with by insurers.
Shortly before 4am last Friday fire crews rushed to the popular Caversham pub.
Smoke and fire were visible from the road, so firefighters responding from Lookout Point and St Kilda immediately put out a second alarm and trucks from Dunedin Central and Roslyn also responded.
Police later confirmed a contractor had raised the alarm.
The contractor arrived at the tavern to clean the fryers in the kitchen, turned them on and left to collect gear from his van.
As he returned he saw smoke and flames.
He then turned everything off, went back outside and raised the alarm, police said.
He saw flames burst through the roof, tiles falling down through the building and firefighters inside rushing to get out, he said.
After firefighters were forced from the building, it took crews about 30 minutes to extinguish the fire with an external attack.
At the height of the fire five trucks, including an aerial appliance, were involved in the effort.
As news of the fire spread, shock and disbelief turned to dismay as patrons reacted to the news on social media.
It is not yet clear if the pub will reopen.
Mr Morris has said that decision rests with the building’s owners.
