Bay of Plenty Coast assistant area commander Scott Bell said the property, located below road level, was "quite difficult" to access.
"From the road area we could see a little bit of flame coming through the roof, but when we went through the property, there were flames all through all levels."
When volunteer firefighters from the Ōmokoroa brigade arrived, back up was called for from Tauranga, Greerton and Katikati. About 20 firefighters worked to control the fire, which reignited shortly after 6am and was still smoking at 8.30am.