Three investigators were at the warehouse yesterday to figure out what caused the blaze.
Fire investigator Greg Hartwell told the Advocate the building did not have automatic fire detection or a sprinkler system.
It was a passing member of the public who saw the smoke, he said.
The cause of the first fire is yet to be revealed.
Brodie Stone covers crime and emergency for the Northern Advocate. She has spent most of her life in Whangārei and is passionate about delving into issues that matter to Northlanders and beyond.