Coronavirus: Health officials unable to yet rule out third strain of COVID-19 in Auckland

Health officials can't yet rule out a third strain of COVID-19 being in New Zealand's community.

Director-General of Health Dr Ashley Bloomfield said on Thursday a case that was originally linked to the Auckland cluster is now reclassified as 'under investigation'.

This person worked in a retailer in Auckland's St Lukes Mall on August 12, the morning the city entered alert level 3 lockdown at midday. They were also in the mall the afternoon of August 12, and also on August 14, 15 and 17.

With this case's reclassification, Dr Bloomfield said it can't yet be ruled out this person represents a new strain of the virus.

"The genomic sequencing is underway at the moment and that will give us the strongest hint about where it might be linked to. So, still under investigation both epidemiologically and the genomic sequencing," he told reporters.

He added the genomic sequencing results are expected either later on Thursday or on Friday morning.

Dr Bloomfield also revealed a lift at Auckland's Rydges Hotel might be what infected a maintenance worker there.

A returnee from the US stayed in the hotel, which is being used a managed isolation facility, at the end of July before testing positive for COVID-19 and being moved to a quarantine facility.

Dr Bloomfield said it was a "matter of minutes" between the returnee and then the maintenance worker using the lift.

"This has been found through the swipe card from the guest and the maintenance worker," he said.

It's currently the only spot that connects the two cases and is, at least for now, the best hope to finding the link between the pair after all the Rydges Hotel nurses tested negative.

"This is now a new and strong line of investigation," Dr Bloomfield said.

Finding the origin of Auckland's cluster and the Rydges' cases is a process of elimination, but the biggest clue for the largest cluster was ruled out. Dr Bloomfield said four swabs at Americold in Mt Wellington found small traces of the virus, but not enough to infect a person.

The first case in this recent outbreak was an employee at the facility.

"It does not appear the contamination of imported chilled packaging is the likely source of infection at this point," Dr Bloomfield said.

"It is more likely and always was likely it was person-to-person. What we haven't been able to do is identify the first person… We haven't got any hints about what came before that and that's what we're trying to establish."