Of the 511 cases in the Delta outbreak, at least 73 of those are essential workers, it has been confirmed.
It comes as 83 new cases were recorded Sunday, 496 cases are now in Auckland, 15 in Wellington.
By 10.00am Sunday, health officials had identified 32,000 contacts. Of those, over 80 per cent had been followed up and more than 85 per cent had a test so far.
Jacinda Ardern says health officials have worked out transmission has occurred at 21 locations of interest to date.
She says over half of Sunday's cases are household contacts of previous cases and two were infectious before Alert Level 4 restrictions were put in place.
A total of 25 people's exposure events were outside of the household, "generally [at] essential worksites" and generally not customer-facing.
Ardern says she's asked health officials to investigate that final point further "so we can assess whether our level 4 rules on who is operating is being adhered to, and whether our public health protocols for those businesses that are operating are fit for purpose".
On Friday, Countdown's general manager corporate affairs, safety and sustainability, Kiri Hannifin said "more than 2000 of our team unable to come into work and over 1000 are still out of action on any given day due to their store being a location of interest, having a household member at a location of interest, not having childcare available or because they are vulnerable to Covid-19".
Foodstuffs head of corporate affairs, Antoinette Laird, last week said hundreds of staff were self-isolating after more than a dozen supermarkets were listed as locations of interest.