The video was given to RNZ by a member of the public.
Foodstuffs North Island chief executive Chris Quin said the fire at the New World store started in a rebuild area, with the supermarket under renovation.
He could not confirm the cause.
Quin said the value of stock loss was unknown, but staff would be looked after and most customers had been reunited with their undamaged cars.
The fire started in the mezzanine roof space and spread inside to aisles.
Fire and Emergency New Zealand said the blaze was under control and crews remained at the scene damping down hotspots.
A stay inside emergency alert was issued for people southwest of the fire but that had since been lifted.
The public has been asked to avoid the area.
– RNZ