KEY POINTS:
The fire that destroyed an Onehunga Mitre 10 store is now thought to be deliberate after investigators failed to find any accidental or electrical causes.
The Fire Service announced yesterday that the investigation into Monday's fire - the biggest blaze in Auckland this year - had ruled out any electrical and accidental causes.
Manukau District Chief Fire Officer Larry Cocker yesterday told the Herald that the area where the fire began - believed to have been on an external wall of a storage area - was 3m away from the nearest electrical appliance or power switchboard.
"They've eliminated all of the accidental possibilities, including electrical," he said.
Fires in two power transformers in nearby streets, which cut power to 579 homes, were a result of the blaze.
"The evidence suggests that the electrical supply to the building was operating normally and there's no evidence to suggest otherwise," Mr Cocker said.
"They've eliminated every other cause and all that remains is that there's a possibility that it could have been deliberate but it's still undetermined, so we've put the file to police for them to eliminate anything of a suspicious nature."
Mr Cocker was surprised by the findings.
"I would have thought, being a fire during the day, the cause would have been quite straightforward - the store was occupied, people were there, someone would have been able to say 'yeah we left something on' or there was a spark from something, but obviously that's not the case and there's still a question mark over the why."
When asked how likely investigators were to find a cause, he said: "I'd like to think that someone will get to the bottom of it but often fires can be just left undetermined - that just happens sometimes - but it would be unusual for that to be the case in a building that people were around."
Mitre 10 chief executive Craig Wilson said the company was shocked by the findings and would be assisting the inquiry team.
The officer in charge of the police investigation, Detective Senior Sergeant Greg Cramer, said a team of three detectives was workingthrough evidence and reports on the fire.
"At this stage, the cause is still indeterminate and I guess that is the reason - by default - that it is deemed deliberate. There is no accidental or natural cause."
It was too early to say if all of the staff in the store would be interviewed. "Obviously there's a number of people that we would like to speak to in some detail and that includes anyone who was in the area at the time," he said.
Police want anyone with information on the blaze to call (09) 524 1932
