UPDATED 7.44PM: At least one property is in danger as a large scrub fire rages on Auckland's west coast.

The blaze broke out just after three this afternoon in bush between Cornwallis and Huia.

One helicopter, eighteen appliances and more than 70 firefighters are battling the blaze, which is about six hectares.

A second helicopter is already on the ground, and a third is being called in.

Additional fire crews have been called in from a number of stations in west and central Auckland.

The Fire Service says one property is at risk and crews have been mobilised to stop the fire getting to it.