New Zealand's Prime Minister Jacinda Ardern said on Saturday that the country's biggest city, Auckland, will go into a seven-day lockdown from early morning on Sunday after a new local case of the coronavirus of unknown origin emerged.This comes two weeks after Auckland's nearly 2 million residents were plunged into a snap three-day lockdown when a family of three were diagnosed with the more transmissible UK variant of the new coronavirus that causes COVID-19.Health officials, who could not immediately confirm how the person got infected, said genome sequencing of the new infection was under way. The patient developed symptoms on Tuesday and is regarded as having been potentially infectious since Sunday, officials said. 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.The lockdown, with Level 3 restrictions, will allow people to leave home only for essential shopping and essential work, Ardern said. Public venues will remain closed. Restrictions in the rest of the country will be tightened to Level 2 restrictions, including limits on public gatherings.New Zealand, one of the most successful developed nations in controlling the spread of the pandemic, has seen just over 2,000 cases of the coronavirus since the start of the pandemic.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 6 in Auckland's harbor. America's Cup Event said on Twitter it was working "through the implications."