A large palm kernel blaze which sent smoke billowing above Mount Maunganui businesses could have started from machinery inside the building.
Fire broke out at the Glencore Grain NZ's southern palm kernel storage sheds on Waimarie St at 9am Sunday.
A Fire and Emergency New Zealand spokesman at the scene said the cause of the fire was possibly machinery-related.
"The cause is not looking suspicious," he said.
Thankfully, no-one was inside the building at the time of the fire and surrounding businesses did not need to be evacuated, he said.
The spokesman said up to 80 fire service staff were called in to help with the blaze and three crews worked overnight to dampen hotspots.
"It is a big operation," he said. "However, we have scaled right back and are running with two crews today. I would like to think by mid-afternoon we will hand it back to the owners."
Crews from Katikati, Te Puke, Greerton, Tauranga and as far as Auckland and Hamilton were called in, he said.
Firefighters could today be seen putting on breathing apparatus and walking into the burned out storage facility, which is blocked by road cones.
The spokesman said the palm kernel is expected to smoulder for some time before heavy machinery can be used to fully extinguish and remove it.
"These products tend to burn slowly. They will smoulder and burn deep," he said.
"What we are doing at the moment is we have machinery in both sheds slowly moving the product back and we are monitoring it with thermal imagery cameras for hotspots. Where necessary we are dampening it down and moving it back."
The spokesman said it was unclear how much of the palm kernel had been damaged but, thankfully, there was only a small amount of product in each of the two sheds.
"One shed nearest to Hewletts Rd was about half full and the far shed also had a small amount of palm kernel inside and soybean meal in the rear," he said.
"Most sheds are quite structurally intact, there has been not a lot of structural damage."
The fire thankfully did not spread to the neighbouring timber yard, he said.
Fire investigator Luke Burgess said the investigation would be lengthy and it would take some time to determine an exact cause.
Port of Tauranga chief executive Mark Cairns said the Glencore Grain NZ's southern palm kernel storage shed had been operating on the site for about five years.
"Fortunately, no one was injured which was our first concern, and did not spread to other buildings or pose a risk to the Port's container operations," he told the Bay of Plenty Times.