Health authorities have revealed the time that the person with the earliest identified case of the Delta variant was in the lobby of the Crowne Plaza Hotel MIQ facility in Auckland.
They say if transmission occurred in the lobby it would have been on Saturday 7 August between 10pm and 11pm.
The Ministry of Health has been trying to track down six people who were in an adjacent walkway at the time.
Of the six, four have been identified using CCTV and three of them have tested negative.
Two are still to be identified.
Those six people were in an open walkway while the person with the earliest identified case of the Delta variant was in the lobby of the Crowne Plaza Hotel MIQ facility in Auckland.
Health officials are investigating if there was a possibility of air flow between the two spaces.
Those going into MIQ go in through the lobby via the atrium, which is a thoroughfare shared by members of the public, but is divided by a perspex barrier.
The thoroughfare is located inside the Crowne Plaza building and is not the outside walkway which is used to access the nearby Huawei Centre.
It has been confirmed the case was indoors while a very small number of people walked in the open walkway, which is well ventilated. The day in question was 7 August.
The Ministry of Health said the atrium was sectioned off from the public in accordance with MIQ perimeter fencing standards.
Associate Health Minister Ayesha Verrall said the chance of the virus jumping between the cordoned off areas was a hypothesis that needed to be tested.
She said all sources needed to be investigated no matter how surprising.
A man whose partner was in the Crowne Plaza Hotel MIQ facility last year said at the time he was surprised how close it was to a public accessway.
Dominic Hartnett said initially there was a plywood barrier, but now it is perspex.
He said it was a thoroughfare used by people to go to shops, restaurants and apartments.
The walkway through the atrium is also used to access a vaccination centre.
The Ministry of Health said the public walkway did pass a fresh air area for returnees but it was separated by fencing with perspex panels and met MIQ standards.