Auckland prepares for lockdown as mystery Covid-19 cases emerge in New Zealand

Officials consider freight as possible source of new coronavirus cluster

New Zealanders on Wednesday scrambled to stock up on essentials as the country's biggest city prepared to go into lockdown again, following new cases of the coronavirus that ended a 102-day record run without any new infections.

Prime Minister Jacinda Ardern announced overnight that she was shutting down Auckland after four new cases of Covid-19 were discovered in the city from the same family, despite the international borders' being shut to foreigners and returning New Zealanders put in mandatory quarantine.

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The government has said the source of the new infections was unknown so far.

Long queues were reported outside supermarkets in Auckland and across other parts of the country, as people raced to stock up on food and other essential items before the new restrictions took effect from noon.

The source of the outbreak has baffled health officials, who said they were confident there were was no local transmission of the virus in New Zealand for 102 days and that the family had not travelled overseas.

"We are working hard to put together pieces of the puzzle on how this family got infected," said Director-General of Health Ashley Bloomfield.

READ: New Zealand announces return of Covid-19 after 102 days

Investigations were zeroing in on the potential the virus was imported by freight. Bloomfield said surface testing was underway in an Auckland cool store where a man from the infected family worked.

"We are very confident we didn't have any community transmission for a very long period," Bloomfield said during a televised media conference. "We know the virus can survive within refrigerated environments for quite some time."

China has reported instances of the coronavirus being detected on the packaging of imported frozen seafood.

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On Tuesday, the city government of Yantai, a port city in eastern Shandong province, said it had found the virus on the packaging of frozen seafood that had arrived from the port city of Dalian, which recently battled a surge of cases. Officials said the seafood was from an imported shipment that landed at Dalian, but did not say where it originated.

New Zealand's biggest city will move back into alert level-3 lockdown, which would mean people should stay away from work and school, and gatherings or more than 10 people would again be restricted. The restrictions will be in effect for three days, until Friday.

The rest of New Zealand will move into level 2, meaning social distancing measures would be applied and mass gatherings would be limited to 100 people.

Health Minister Chris Hipkins told Radio New Zealand on Wednesday that the government was considering making wearing mask mandatory for Aucklanders.

READ: New Zealand reaches 100-day milestone without coronavirus transmission

New Zealand's successful fight against Covid-19 was hailed globally, and the Pacific island nation of five million was seen as one of the safest places, as the pandemic raged globally.

It marked 100 days without a domestic transmission of the coronavirus on Sunday but warned against complacency as countries like Vietnam and Australia which once had the virus under control now battle resurgences.

Calls have grown to postpone the national election scheduled for September 19, as political parties suspended campaigns due to the new restrictions.

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"It's going to be very difficult to have an election in mid-September when we are now mid-August," opposition National Party leader Judith Collins told Newshub.

Ardern, who is seen winning comfortably, according to opinion polls, has said she has not yet considered the impact of the new restrictions on the polls.