A person living in the north of Auckland has tested positive to Covid, according to emails from a property management group.
The notices advise owners at The Grange development in Albany that they are now considered casual contacts of the new Covid case.
It is also understood a notice was put in letterboxes in nearby homes advising of the positive case.
One resident, who did not wish to be named, said she was informed of the positive case by The Grange bodycorp on Wednesday.
"My understanding from talking to different people [within the complex] since then is that person is now in MIQ," she said.
She said she didn't know who the person was, with those living in the complex keeping to their bubbles throughout the lockdown.
"It is a very big complex and because of privacy they can't tell us who or where it is," she said.
"But a number of people have gone out and had Covid tests just to be on the safe side."
She said her own Covid test had come back negative.
There does not yet appear to be any Albany buildings or shops listed among the Ministry of Health's Covid locations of interest.
The Ministry of Health would not confirm whether it was aware of a new case in Albany.
"We don't comment on speculation and rumour," a spokesman said.
"Confirmed cases of Covid-19 are announced at 1pm each day."
The Grange development contains a mix of more than 100 apartments and townhouses and has its own communal tennis court and swimming pool.
A notice sent by Crockers Property Management to residents said Auckland Regional Public Health had informed them "that residents at The Grange are classified as Casual Contacts".
"Casual contacts are people who have been in the same place (location of interest) at the same time as someone infectious with Covid-19," the notice read.
Casual contacts are considered at low risk of getting sick with Covid, it said.
Crockers said that because of privacy laws it could not give out details that might identify the affected resident.
"Please do not ask for details on the unit number, floor level or other identifying information for this resident - we cannot share this information with you," it said.
"Thank you for approaching this developing situation with a sense of empathy, patience and understanding."
The Crockers notice also asked residents to remain calm and follow advice given by health teams.
That included regular hand-washing and social distancing.
"Wear gloves and mask when putting out the rubbish today as a deep clean of the bins has been arranged take place once the bins have been emptied tomorrow."
The company also asked residents to get tested if they have Covid-like symptoms and to please inform them if they tested positive.
The security guard was critically injured and remains in hospital after surgery overnight.