“Our enquiries are still in the early stages, which will include reviewing available CCTV footage and speaking further to any witnesses.
“We continue to keep an open mind as to why this event occurred.”
A Fire and Emergency New Zealand spokesperson said an automatic fire alarm activated at 1.40am on Sunday.
The road was blocked while Fire and Emergency worked, and a fire investigator was called to the site.
Hato Hone St John said one person was treated at the scene for smoke inhalation.
A fire investigator was called to the site.
Anyone with information that could assist our enquiries can update Police online now or call 105 using the reference number 251123/9438.
Information can also be provided anonymously via Crime Stoppers on 0800 555 111.
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