Human error allowed two passengers to accidentally enter a "green zone" at the Brisbane International Airport after arriving on a flight from Papua New Guinea.

The pair were in the area for an hour-and-a-half, shopping and using public toilets, before being retrieved by airport staff.

Initial test results from one passenger for COVID-19 came back negative and the second passenger's test was inconclusive – but more samples sent to Queensland Health's Forensic and Scientific Services laboratory have since confirmed that he is COVID-positive.

While the pair were in the green zone, three New Zealand flights took off with around 390 passengers – these were Air New Zealand NZ202 from Brisbane to Christchurch, Air New Zealand NZ146 from Brisbane to Auckland, and Qantas QF135 from Brisbane to Christchurch.

Chief Health Officer Dr Jeannette Young said the pair posed a low risk to others.

“While at the airport, they wore masks and socially distanced and neither has reported symptoms," she said.

“They were in the wrong zone through no fault of their own and we appreciate their patience and cooperation while we rule them out as cases.

“We’re also grateful for the prompt action by Brisbane airport staff once the mistake was identified.”

In a statement from Brisbane Airport Corporation, the airline has "unreservedly apologised".

"At approximately 9:30am, two transit passengers arrived on a 'red' flight from Port Moresby and proceeded through screening to transit as per normal process," a BAC statement said.

"Initial review of CCTV indicates that at approximately 9:55am, these passengers were incorrectly allowed into the 'green zone'.

"The breach is due to human error, and BAC is currently working with all relevant authorities including Queensland Health to investigate the circumstances of the breach."

"BAC is conducting a thorough investigation and unreservedly apologises for this human error," the statement said.