People in seven key Auckland suburbs are being encouraged to get a Covid-19 test even if they have no symptoms.
Mt Eden, Massey, Māngere, Favona, Ōtara, Papatoetoe and Manurewa are under increased scrutiny by health officials because of their links to mystery cases or clusters that may have unexpected cases.
Counties Manukau District Health Board chief executive Margie Apa said it was most important they get tested if they had symptoms - but they also wanted people without symptoms to come forward.
"We have continued to see a small number of unlinked positives cases - these are cases where the person has not visited known locations of interest, has not already been identified as a contact of a positive case, and they have not always had typical or obvious Covid-19 symptoms," she said in a statement.
"We want to cast a wide geographical net around the location of known clusters and unlinked cases so we particularly want to see more families and household bubbles from seven Auckland suburbs of interest come out to get tested."
The surveillance testing would help them find out whether there were any undetected chains of transmission, Apa said.
People who do not have symptoms and get a one-off Covid-19 test for surveillance purposes do not need to isolate while they wait for the result.
Four hundred extra testers have been trained in the past few weeks to help in Auckland.
Today, the Ministry of Health confirmed 33 new community cases of Covid-19, all in Auckland.
There were 4250 Covid-19 tests done in Auckland in the last 24 hours - with the total number of tests done nationwide during that time at 8657.