Meikle said the advice to residents to stay inside and away from the area remained, but added there were no public health and safety concerns.
"There is no danger to the public at all," he said.
The fire had died down considerably, Meikle said, but he expected crews to be involved for most of the day.
A police spokeswoman said the circumstances of the incident were still unclear, and no charges had been laid as yet.
Last night, 12 fire trucks attended the fire, including two water tankers, a command unit and incident support unit.
People watching the fire had been told to leave and go home by the New Plymouth Fire Service as the smoke from the fire could be toxic.