Delays are expected at airports across Australia after a bizarre security breach in Melbourne earlier on Tuesday.

Travellers were hauled off at least one flight just seconds before it was due to depart and faced long delays after a lone passenger apparently “inadvertently passed from an ‘unscreened’ area to a ‘screened’ area of the airport”, according to a Qantas spokesperson.

They did now say how the passenger managed to get from one area to another.

“As a precaution all Qantas operations have been put on hold and passengers in the terminal are being rescreened, which is causing delays to some services this morning,” they said.

“Safety is our No.1 priority, but we know this disruption is causing some inconvenience for our passengers and we apologise for that. We are investigating how this incident occurred.”

After the breach about 6am on Tuesday, federal police shut down a section of the domestic terminal and ordered passengers from a plane that was ready for take-off.

Passengers were being “rescreened” after the apparently accidental breach.

Social media posts showed long queues at the Qantas checkouts in terminal 1.

Security breach at QANTAS Melbourne domestic terminal. Shutters closed and people already cleared evacuated back out front. No news about the breach. At one point we were asked to leave the building but that order was rescinded.#QANTAS #Melbourne pic.twitter.com/8riqCgxqfW

— Nathan Berry (@nateintokyo) October 10, 2022

“Shutters closed and people already cleared evacuated back out front,” Nathan Berry posted on Twitter.

“No news about the breach. At one point we were asked to leave the building but that order was rescinded.”

Tim Joyce told the ABC he was seated on a flight that was just a minute from taking off when passengers were all told they had to get off.

Mr Joyce said later there were “thousands of people” waiting in the terminal to be rescreened.

Another passenger on the same flight said they were waiting to push off when the breach was announced – and everyone was told to head back into the terminal.

“Qantas keeps sending messages saying, ‘It will be 10 minutes’. But at the moment we are actually in a queue to be rescreened,” Sue Duke told Seven’s Sunrise.

“We’re going to Brisbane and hoping to get a connecting flight to Norfolk Island. We are hoping that Qantas will hold the flight.”

In a post on Twitter about 7.30am, Melbourne Airport officials said screening of passengers in T1 had resumed.

However, delays were expected to last throughout Tuesday morning, with knock-on effects across Australia.