Up to 1000 people had to be rescreened at Auckland Airport after a power cut to a metal detector.

Passengers at Auckland Airport are finally boarding their planes after significant delays from a power cut to a metal detector on Wednesday night.

That was after security re-screened up to 1000 people who had already passed security – and in some cases had already boarded their flights.

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DILEEPA FONSEKA/STUFF Former Labour leader David Shearer, who was trying to get to Kenya, said passengers weren't being given enough information about the delays.

The airport tweeted just before 8pm that flight security provider Aviation Security had "temporarily halted" screening on international flights.

"We are working with them to resolve this as soon as possible."

Aviation Security spokesman Mike Richards said there was a "power supply interruption" to one of the metal detectors at the screening point.

DILEEPA FONSEKA/STUFF Internet Explorer crashed on the airport's departure boards during a chaotic night for travellers.

"When it was discovered we realised that 53 passengers had gone into the terminal without being screened. We had to call them back and re-screen them."

Unfortunately, there was no way to distinguish those passengers from others in the terminal, so everyone had to be called back, Richards said.

That included people sitting on flights waiting to depart, shopping in duty-free stores or queueing to board planes.

GRANT BAXTER/SUPPLIED All passengers in the international terminal had to be rescreened by security.

"If you hadn't left the terminal, you would be considered effectively one of the people who hadn't been screened, so you'd have to come back through."

It was a "really big job", he said.

"[They're] unfortunate circumstances, but unfortunately we have to put safety and security ahead of the timetable."

MIKE DALEY/SUPPLIED Massive queues formed at Auckland Airport after a power cut to a metal detector.

Auckland Airport spokeswoman Kate Thompson said at 9.30pm the decision had been made "in the last hour" to hold all international flights.

The airport had brought on a "few extra" staff to cope.

More than 1000 travellers had been affected, she said.

DILEEPA FONSEKA/STUFF Police had arrived at Auckland Airport to hand out departure cards and keep order.

"Our main concern here is to get passengers away as soon as we can."

Thompson was certain sure exactly how many flights had been affected.

About 10.30pm, planes began boarding again and airport staff started calling passengers on specific flights to come through security.

MIKE DALEY Passengers on every flight due to depart from Auckland Airport were being told to "relax", even though some were already scheduled to have departed.

"Please move forward slowly and calmly. We are processing people as quickly as we can," the announcement said.

Police had arrived at the airport and were handing out departure cards and keeping order.

DETECTOR OFF FOR 'ONLY A FEW MINUTES'

Richards said the detector was probably out of action for "only a few minutes".

The fault had been noticed by one of the officers, who noticed the detector had not beeped in a while.

"He checked it and saw that the power was off."

That happened sometime between 5.30pm and 6pm, but Richards could not provide a more exact timeframe.

He said he was not sure what had caused the fault, but believed it may have had something to do with a power cord being disconnected.

The airport had 1500 cameras in total, and footage was quickly reviewed to see "at what point things changed", Richards said.

That was how the figure of 53 passengers was arrived at.

He said "every single person" in the terminal was called back for re-screening.

At 10.15pm, Richards said that process had been completed. The backlog at the airport was being caused by more passengers arriving, he said.

Screening for long-haul flights had been prioritised and "it's just a matter of getting the big international flights out of the way first", he said.

"If you've got a 15- or 17-hour flight ahead of you we're trying to get you away as quickly as we possibly can."

An investigation into the incident would take place at a later date, Richards said.

PASSENGERS FACED LENGTHY DELAYS

Some passengers made it all the way to the departure gate and some had even boarded their flight to the United States when the metal detector fault was discovered.

Mike Daley said boarding of some passengers for his NZ6 flight to Los Angeles had already begun when an announcement came.

Daley said he and his fellow passengers were left waiting for more than 90 minutes after the announcement, with no communication from airport or Air New Zealand staff.

"The board's not updating. My flight says 'gate closed' even though it has not departed."

A queue of passengers waiting to be rescreened was being formed all the way back past the international airport's escalators and duty free areas.

"They're doing the best they can, but it's just an awful situation. There are no good solutions," Daley said.

His flight had been delayed by two hours and 30 minutes. It was originally supposed to depart at 7.30pm, but was rescheduled to depart at 10pm.

Six uniformed staff standing around talking to each other. No one talking to the hundreds in the queue. Maybe no one knows what's happening. — Simon Hoyle (@SimonDHoyle) October 11, 2017 Aviation Security are having to re-screen all passengers. We appreciate your patience during this process. — Auckland Airport (@AKL_Airport) October 11, 2017

Unfortunately we do not have a timeline on this but understand that Aviation Security are working as quickly as possible. — Auckland Airport (@AKL_Airport) October 11, 2017

Another passenger said the whole international terminal had been evacuated and queues were forming in the arrivals area.

Businessman Steve Latta said he was relaxing in the Koru Club, waiting to board a flight to Vancouver, when the whole room was "marched out" and escorted to the transfer centre.

"We have now all formed a very long line and have not yet commenced the walk back through the X-ray machine."

He had been told all flights were delayed for two hours, he said.

FRUSTRATION IN THE QUEUES

Former Labour leader David Shearer, who now heads the United Nations' peace keeping mission in South Sudan, said he was waiting for a flight to Nairobi, via Dubai.

He said the queue had barely moved for two hours.

"A lot of people are foreigners who don't understand English. They could be a whole lot clearer telling people their flights are delayed and what the problem is."

Shearer said he had not encountered anything like this before, and the only information passengers received were through media alerts and updates from Stuff.

Passenger Grant Baxter said there were a "lot of frustrated people" held up in the delays.

The airport was not providing any further information than a repeated announcement that hadn't changed.

The announcement said: "All passengers please vacate the departures area, thank you."

He estimated there were about 300 to 500 people waiting in the area where he was located and they were just those passengers waiting to board flights to San Francisco and Los Angeles.

People waiting for other flights were being detained in other areas.

He said he thought it was strange that no-one had noticed the outage.

A passenger, who wanted to be identified only as Benjamin, said he had been waiting in the line for an hour.

His flight to Shanghai was originally set to depart at 11.59pm. He had arrived about 8.30pm, thinking he would give himself time to go in early and relax in the duty-free area.

He said he had sympathy for airport staff, who he said must be under a lot of pressure, but said he couldn't really hear the announcements coming over the intercom.

Kerry, who also did not want her last name used, had been waiting for her flight to Los Angeles that was set to depart at 9.50pm.

"I am a bit disappointed that there has been no communication," she said.

She arrived at the airport to find a queue already forming.

No staff at the airport had told her anything, she said.