New Zealand has recorded four new cases of coronavirus after 101 days free from community transmission of Covid-19.
Four members of the same family have tested positive for the disease and Prime Minister Jacinda Ardern has brought lockdown measures back into place.
People in Auckland - 1.6million people - have been told to stay at home for 72 hours from Wednesday.
The rest of the country will have to comply with level two lockdown - enhanced social distancing and a limit on the number of people gathering together.
Contact tracing is now being undertaken to find those the family has been in touch with.
Close contacts have been told to self-isolate.The family has no links to overseas travel or travellers.
A man in his 50s from Auckland has tested positive for the disease twice, along with his wife and two pre-school children.
Ms Ardern said: "We have not yet been able to determine the source of these cases, there is no known link to hotel quarantine.
"One of the most important lessons we have learned from overseas is to go hard at this... in line with our precautionary approach, we will be asking Aucklanders to take swift lockdown."
She added: "You are asked to stay home in your bubble unless you are an essential worker."
Auckland's bars, pubs and restaurants will close at midday on Wednesday and gatherings will be limited to 10 people.
Schools will also close.
Face masks will be mandatory in Auckland.
New Zealand Director General of Health Ashley Bloomfield said: "If we are not able to identify the source, we should be able to identify whether we have wider geographic spread.
"We have been saying for some weeks that it was inevitable that New Zealand would get another case of community transmission."
