Smoke alerted a passerby to a fire in the veranda above Starbucks in central Tauranga.
Firefighters were called to the building just after 5am.
Tauranga Fire Brigade senior station officer Kevin Cowper said the crew arrived to find burning in the void above the veranda.
The crew had to punch a hole in it to get to the fire inside.
AdvertisementAdvertise with NZME.
"It had probably been smouldering away for hours," he said.
The cause of the fire was still being determined but early indications were it was electrical, he said.