New Zealand’s largest city of Auckland will go into a three-day lockdown beginning just before midnight Sunday following the discovery of three unexplained coronavirus cases in the community.

Prime Minister Jacinda Ardern announced the move after an urgent meeting with other top lawmakers in the Cabinet. She said they decided to take a cautious approach until they find out more about the outbreak, including whether the infections are of the more contagious variants.

The lockdown is the first in New Zealand in six months and represents a significant setback in the nation’s largely successful efforts to control the virus. It will also force a delay in the America’s Cup sailing regatta.

New Zealand had successfully stamped out community spread, and many people elsewhere in the world looked on in envy as New Zealanders went back to work and began attending concerts and sporting events without the need to wear masks or take other precautions.

Indeed, Ardern on Sunday had planned to attend the Big Gay Out, an Auckland festival that celebrates the rainbow community and attracts tens of thousands of people. She ended up canceling those plans and returning to Wellington to manage the outbreak.

“I’m asking New Zealanders to continue to be strong and to be kind,” Ardern said at a hastily arranged press conference on Sunday evening. “I know we all feel the same way when this happens. We all get that sense of ‘Not again.’ But remember, we have been here before and that means we know how to get out of this again, and that is together.”

New Zealand’s greatest vulnerability has been at the border.

New cases are regularly caught among returning travelers, all of whom are required to spend two weeks in quarantine. Despite precautions, there have been several times when the virus has leaked out from the border before being controlled again, and officials are trying to determine whether that’s happened again.

In the latest case, an Auckland mother, father and daughter caught the disease. Officials said the mother works at a catering company that does laundry for airlines, and officials are investigating whether there is a link to infected passengers. Officials said the woman hadn’t been going aboard the planes herself.

Officials said the rest of New Zealand outside of Auckland will also be placed under heightened restrictions, although will not go into lockdown.

“We are gathering all of the facts as quickly as we can, and the system that served us so well in the past is really gearing up to do so again,” said COVID-19 Response Minister Chris Hipkins.

He described the cases as new and active. He said scientists are carrying out genome sequencing to see whether they are variants, and also to see whether they match with any infected passengers.

“New Zealand has kept COVID-19 contained better than almost any other country,” Hipkins said. “But as we have kept saying, there is no such thing as no risk.”

New Zealand, with a population of 5 million, has reported a total of just over 2,300 cases and 25 deaths since the pandemic started.

The country has been hosting the America’s Cup sailing regatta. Racing was due to continue on Wednesday in the Prada Cup challenger series, but organizers have announced that a postponement will be necessary. Italy’s Luna Rossa Prada Pirelli leads Britain’s INEOS Team UK 4-0 in the first-to-seven series. The winner will then take on Emirates Team New Zealand for the America’s Cup.

(AP)