"The smoke is dissipating now,'' he said.
Underwood said six fire crews remained on site as the job had been classified as a second-alarm response.
A spokeswoman for Auckland Airport said airport emergency services and Fire and Emergency NZ staff were now investigating the "sighting of smoke at the international airport'' this morning.
A more detailed description of what had happened is due to be released later this afternoon, she said.
The incident had not led to any disruptions or cancellations of flights, she said, and no one had to be evacuated.
St John said they were notified by FENZ of an incident at Ray Emery Dr at 11.50am. However, they were not required.
This morning's scare comes after a fire drill was carried out at the Auckland Airport early this morning.
