New Zealand’s Prime Minister Jacinda Ardern announced on Saturday that the country’s biggest city, Auckland, will go into a seven-day lockdown starting early Sunday morning after a new local COVID-19 case of unknown origin emerged.

This occurs two weeks after Auckland’s nearly 2 million residents were plunged into a three-day lockdown when a family was diagnosed with a more transmissible U.K. variant of COVID-19. Health officials could not immediately confirm how the person got infected, but have said that the genome sequencing of the new infection was under way. Officials said the patient developed symptoms last Tuesday and is regarded as having been potentially infectious since Sunday. The person has visited several public venues during that period.

“Based on this, we are in the unfortunate but necessary position to protect Aucklanders again,” Ardern said, announcing the lockdown.

Health authorities were trying to find out whether the new case was linked to the earlier February cluster, now at 12 infections.

Auckland’s lockdown will include level 3 restrictions, which will allow people to leave home only for essential shopping and essential work. Public venues will remain closed. Restrictions in the rest of New Zealand will be tightened to Level 2 restrictions, which will put limits on public gatherings.

New Zealand has been one of the most successful developed nations in controlling the spread of the pandemic. The country has only seen over 2,000 cases of COVID-19, and has had a death toll of 26 since the start of the pandemic back in 2020.

A marquee Twenty20 cricket clash in Auckland between New Zealand and Australia, scheduled for Friday, will be played in Wellington without crowds, said New Zealand Cricket. The new restrictions also complicated the America’s Cup Event yacht race scheduled to start on March 6th in Auckland’s harbor. America’s Cup Event said on Twitter it was working “through the implications.”