Fire crews are sniffing out a bad smell hovering over Auckland Airport's airfield.

Six fire crews from nearby stations have responded to the call which came in about 9.30am.

Northern Fire Communication shift manager Jaron Phillips said some of the smell had wafted from the runway into airport buildings.

Emergency services were checking a number of areas on and off the airfield, and had ruled out the possibility of a ship unloading fuel nearby. They were now looking into a construction site and some small LPG reserves.

He said an evacuation was unlikely as the smell seemed to be dissipating.

Mr Phillips said if anyone in the area was concerned, he urged them to call the fire service on 111, but it appeared that the smell is dissipating.

Emergency services had ruled out the possibility of a ship unloading fuel nearby as a source of the smell and were now looking into a construction site, and some small LPG reserves.