The Ministry of Health said this evening that two other people who completed managed isolation at the Pullman Hotel at the same time as the Northland community case were now under investigation.
The pair were asymptomatic and had previously returned two negative tests, the ministry said.
Both were isolating at home.
As a precaution, Public Health staff are checking details with the individuals about their movements since they left managed isolation to identify close and casual contacts if contact tracing is required.
"The two former returnees both returned a positive test for Covid-19, however it is yet to be confirmed if they are recent or historic infections. Further urgent testing is being carried out this evening."
A 56-year-old woman from Northland tested positive for Covid-19 on Sunday. All her close contacts have since tested negative.
She left MIQ on January 13, developed mild symptoms on January 15 and was tested on January 22. The woman visited 30 locations of interest across southern Northland including retail outlets, restaurants, cafe and supermarkets.
Epidemiologist Michael Baker said the pair could be weak positive cases and it was most likely that they were historic cases.
"Weak positive", he said, usually means they were exposed to the virus, perhaps months ago, and got infected and got over it.
"They've still got fragments of the RNA from the virus left in their respiratory systems and this is being picked up."
"It's up to the people on the ground to manage this and they are treating these as though they are potential cases. That's the right thing to do. They'll work through this and work out if there is anything to worry about."
Baker said it was not unusual when lots of people were tested with a very sensitive test.
"A portion of those people who've been previously infected and by chance, will turn up weak positive results."
He said he understood the difficult position the Ministry of Health was in when choosing what to report to the public.
"I like them erring on the side of reporting, rather than not reporting when they see things, but this must be quite a hard decision for them, it's obviously going to cause people a lot worry."
She had spent two weeks in MIQ at Auckland's Pullman Hotel. She left MIQ on January 13, developed mild symptoms on January 15 and was tested a week later on January 22.
The woman visited 30 locations of interest across southern Northland including retail outlets, restaurants, cafe and supermarkets.
Earlier today director general of Health Dr Ashley Bloomfield said there were "encouraging signs" in Northland but the situation was still unfolding.
"We're not breathing out just yet."
The close contacts of the Northland woman will remain in isolation for the full 14 days despite testing negative.
The 353 guests at the Pullman Hotel at the same time as the woman are being contacted and tested - so far all staff and guests have tested negative.
There are also four new cases in managed isolation facilities today. The total number of active cases is 68 - including the one in the community.
