The blaze that tore through a packhouse in Rangiuru is under investigation as firefighters work to put the fire out.

Reports of the Oakside Coolstore and Packhouse blaze first came in about 12am and firefighters are still at the scene.

Around 15 fire trucks and five tankers were needed to help get the fire at the Oakside Coolstore in Rangiuru under control.

Northern Fire Communications shift manager Scott Osmond says the building where the fire started is about 200m by 200m and the fire was in about one third of the building.

'The fire is now under control but it's not out. We have a digger coming to clear some of the roof that has fallen so that we can get it out completely.

'It was a third alarm; meaning there was about 15 fire trucks and five tankers.”

The cause of the fire is under investigation.