Another resident who wished to remain anonymous said contractors had been working to re-strengthen the building for more than a year.
In a typical kiwi fashion, other keen watchers pulled out their deck chairs and enjoyed a cool beverage in the sunshine while watching the commotion, while others continued playing touch rugby in the front yard.
A contractor who had been at the scene for more than an hour said the building seemed to have worsened over a short period of time and said engineers were continuing to survey the site.
Unison relationship manager Danny Gough said they made the call to disconnect power to the surrounding area just before midday.
"We were notified by the police shortly after the incident happened and they were concerned for public safety in terms of the stability of the building and the surrounding properties.
We've de-energized the power purely in the interest of public safety, in case the building did fall across existing powerlines or collapsing among itself creating a fire within its own electrical system.
About six customers have been affected and we're hoping to have the power back on just after 3pm," he said.
Police were assisting with traffic control and an officer said he was unsure of how long they would be at the scene.
"It's so unstable it could potentially give way, power has been cut off for that reason," he said.
The building is leased by Polarcold and CEO Steve Foote said no staff members were in the building when it collapsed and the building will remain cordoned off to protect members of the public.
"None of our staff or contractors were in there or on the site, so there's no implications for health and safety and that was our number one concern.
This is an issue for the building owner and he'll be talking to his consulting engineers and they're working through the problem with the building."
Foote said the warehouse was used to store frozen goods.
