Firefighters are appealing for Northlanders to be careful where they throw their cigarette butts after a grass fire near a Marsden Point oil refinery.
It took nine fire crews and a helicopter to put out the fire on scrub and grassland on Marsden Point Road this afternoon.
Refinery spokesman Greg McNeill said the fire spread over two hectares at its peak, forcing the evacuation of a small nearby workplace and the partial closure of the road.
Rural fire manager Trevor Bullock said the fire had the potential to be very dangerous.
The cause of the fire was not confirmed, but Mr Bullock said the area was bone dry and a carelessly thrown cigarette butt could easily have ignited it.
Fire crews would monitor the site overnight to ensure underlying peat soils were not smouldering.
New Zealand Refining staff first spotted the blaze on monitoring cameras and had company firefighters on the scene within 10 minutes.
They were joined by brigades from around Whangarei, as well as a helicopter and bucket crew.