An old parachute-style distress flare is believed to have started a fire that took less than five minutes to change from a small flame to a blaze the size of a football field.

Firefighters are urging Northlanders to wake up to a very real danger after the fire in Ruakaka on Thursday night. About 20 houses in the Paradise Shores subdivision were threatened as the fire raged on neighbouring Department of Conservation land.

Ruakaka Fire Brigade Station Officer Jeff D'Ath said good firefighting skills, and good luck in the form of a sudden drop in the wind that had rapidly spread the fire, contributed to it being put out with no loss of property or injury.

The speed at which the blaze spread over an area about 60m by 60m, with other fires breaking out as a mild wind sent cinders flying into dry scrub, had shocked even experienced firefighters.