An airport spokeswoman said at 1pm the NZDF Explosive Ordnance Disposal unit was due to arrive at the airport to assess and respond to a report of what appears to be an explosive device.
Passengers were ushered off a grounded plane and people were evacuated from the airport buildings as emergency services responded to the threat, which was reported about 8.40am.
The passengers disembarked from the Star Alliance plane and walked across the tarmac to the far car park at the airport, where police remain stationed outside the main terminal.
A police spokesman said they received a report "of what appears to be an explosive device", and the terminal was evacuated as a safety precaution.
He said the Defence Force bomb squad had been called in.
In an update about 11.15am an airport spokeswoman said it would remain closed while authorities work through a risk assessment process.
"This is likely to take several hours.
"Passengers and members of the public are asked to stay away from the airport until we have clearance to reopen."
"This will disrupt travel plans, so if you had flights booked today, please contact your airline for further information and to rebook."
The airport earlier said on Facebook it had activated its emergency security protocols in response to "a potential bomb alert".
“Emergency services were called and the airport terminal has been evacuated as a precaution while the situation is being investigated by NZ Police and Aviation Security.”
“Airport staff are working with airlines to ensure the safety of all passengers.
“All inbound aircraft have been diverted. All passengers due to depart Queenstown today, and those expecting to meet incoming flights, are asked not to come to the airport until advised otherwise.
"We apologise to our passengers for the disruption, especially as this has happened at the end of the busy school holidays period. Safety is our number one priority and we are working with the relevant authorities."
In a statement, Air New Zealand said the incident had resulted in four flights being cancelled and one flight returning to Christchurch.
"We apologise to our passengers for the disruption, especially as this has happened at the end of the busy school holidays period. Safety is our number one priority and we are working with the relevant authorities."
"I've checked Qantas there's nothing happening there yet, but I've checked with some friends and they're saying something about a bomb, that's all I know so I presume what they'll do is clear the airport, just depends how long it's going to take for that to happen."
Geoff said he was relaxed about his flight possibly being delayed as he had somewhere to stay, but he felt sorry for those who were trying to leave and had flights to make or nowhere to stay.
Himanshu and Jahnavi were due to fly to Wellington but missed their 10.15am flight due to the disruption.
HImanshu said the airport was already in the process of being evacuated when they arrived there at 9.30am.
His wife, Jahnavi, said they were told they had to park elsewhere when they first arrived and then when they walked back, they could not enter the terminal and people were milling around.
"We were asking everyone 'what's happening', 'how long do we have to wait'."
"We got information on our way down at about 8.45am that the evacuation had taken place, and we arrived here at 10am to find all these people milling around, and this is as far as we've got at the roundabout, we've been turned back so we can't get any further."
- additional reporting RNZ
