Foodstuffs property project manager Neil Zonneveld said crews were cleaning New World Gardens on Opoho Rd today.
The store would most likely be open at the usual time tomorrow, although there might be a residual smell inside the building.
The fire originated from a produce cabinet, he said.
A Fire and Emergency New Zealand (Fenz) spokesman said crews from Willowbank were at the called to the scene by an alarm activation about midnight.
The building was heavily smoke-logged.
Sprinkler systems contained the fire, and crews worked to ensure the site was safe.
A fire investigator was notified, he said.