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The fire in a forest off the Coatesville-Riverhead Highway has been contained.
Police are now investigating whether it was deliberately lit. The fire - 200m into the forest off the road - was discovered by a walker.
The fire, which is 150m long and 200m deep in the Riverhead Forest, is believed to have started just before 7.30am.
Firefighters called on the New Zealand Air Force to help with foam and a helicopter to dump water from monsson buckets but they were not needed.
