The Prime Minister says Auckland will move back into COVID-19 alert level 3 and the rest of New Zealand to level 2 after the emergence of a new community case.
The alert level changes take place at 6am on Sunday and will last for at least seven days.
The new case is the older sibling of a Papatoetoe High School student who is a casual-plus contact.
Interviews are now underway to establish how the case was infected.
The Papatoetoe High School student had previously returned three negative tests for COVID-19 and is asymptomatic.
Prime Minister Jacinda Ardern and Director-General of Health Dr Ashley Bloomfield announced the level changes during an impromptu press conference on Saturday night.
Ardern said if a person-to-person link cannot be made, that is a "significant issue".
Auckland only came out of lockdown on 18 February but here is a reminder of what the alert level increases mean for you.
What alert level 3 means for Auckland
The coronavirus response is escalated to alert level 3 if there are multiple cases of community transmission.
The most important measure is the return to the 'bubble' system. Aucklanders are instructed to stay in their bubbles other than for "essential personal movement" such as going to work, school (if necessary) or low-risk recreation.
The bubbles are made up of those in your immediate household but can be expanded to connect with close whānau, to bring in caregivers or to support isolated people. However, it should remain exclusive.
Physical distancing will come back into force too, with two-metre distances advised outside your home or one metre in controlled environments like workplaces.
Schools and Early Childhood Education centres can open but will have limited capacity, and attendees should stay at home wherever possible.
Businesses will not be allowed to offer services involving close personal contact, unless it is a supermarket, primary produce retailer, pharmacy, petrol station or hardware store providing goods to trade customers, or an emergency.
Other businesses can open, but physical interaction with customers is prohibited.
Public venues, such as libraries, cinemas, museums, food courts, gym and playgrounds will be closed.
Gatherings of up to 10 people are allowed only in the case of weddings, funerals and tangihanga, with physical distancing and other public health measures mandatory at these events. Gatherings beyond this 10-person limit are not allowed under any circumstances.
Healthcare services must use non-contact consultations where possible, and people at high risk of severe illness are encouraged to stay at home.
Auckland's border will be closed, but Prime Minister Jacinda Ardern said people can travel through the border if their home is in another region or their travel is essential.
What alert level 2 means for the rest of New Zealand
The coronavirus response is escalated to alert level 2 if limited community transmission could be occurring.
At this level, there are no household bubbles. People are allowed to connect with friends and family in groups of up to 100. Gatherings beyond this 100-person limit are not allowed under any circumstances.
People can also go shopping or travel domestically (outside of Auckland) as long as they follow public health guidance.
Physical distancing of two metres from people you do not know is advised, with one metre of distancing in controlled environments like workplaces.
Businesses can open to the public so long as they follow physical distancing and record-keeping rules, and alternative ways of working are encouraged where possible. Hospitality businesses must keep groups of customers separated, seated, and served by a single person.
Sport and recreation activities are allowed, and public venues like museums and libraries are allowed to remain open. Event facilities like cinemas and stadiums are also able to open, so long as no more than 100 people are in a single confined space.
Schools, universities and early childhood education centres can also remain open, and health and disability services are allowed to operate as normal.
Face coverings are required on all public transport.
Those at high risk of severe illness are encouraged to take additional precautions when out and about.
