An investigation into the cause of a major fire at a recycling plant on Auckland's North Shore will begin at first light on Friday.
Fire and Emergency NZ said the large fire on Hillside Road, Wairau Valley was brought under control by 11.30pm on Thursday.
Assistant Commander Barry Thomas said the incident had been scaled down to a "second alarm" and fire crews were working to extinguish hot spots using ladder trucks.
"There is significantly less smoke, but it continues to affect communities in Glenfield and Witheford Heights," he said.
"We advise people to stay inside and to keep windows closed if they smell or see smoke."
At least three fire trucks would monitor the fire and work to cool the interior overnight, Thomas said.
"We'll start work with heavy machinery in the morning."
The cause of the fire was not known.
Fire and Emergency earlier said it was understood there were batteries on fire inside the factory.
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