Police had suspended all flights to "ensure the safety and security of everyone on Auckland Airport's precinct".
A Defence Force spokesperson confirmed a bomb squad was at the scene.
"The New Zealand Defence Force can confirm that the NZDF Explosive Ordnance Disposal team has responded to a request for assistance from New Zealand Police at Auckland Airport. No further details will be released."
Members of the public heading to the domestic terminal were told to use Tom Pearce Drive instead.
Motorists were also warned to expect delays.
"Police appreciate motorists' co-operation ahead of time as we conduct those inquiries at the location.''
Mayank Batra, an operations controller at Swissport Executive Aviation across the road, said the Air New Zealand Airport Campus was being evacuated.
His colleagues were not being allowed down Geoffrey Roberts Rd. Police were telling them there was a bomb threat in the campus carpark.
Batra could see 6-7 police cars and a fire truck. His building was also being evacuated.