Covid-19 Alert Level 3 restrictions are being extended for Northland and the majority of Waikato.
The restrictions will be in place for another five days, until at least 11.59pm Monday, October 18.
The regions' levels will be reviewed, along with Auckland, also on Monday.
Covid-19 Response Minister Chris Hipkins said there was a worry people who could have been infected and may be symptomatic may be reluctant to come forward to get tested in Northland, and there was two unlinked cases in Waikato.
He stressed that any information gathered during the Covid testing process would be used to stamp out Covid and it would not be used for any other purpose.
There was 55 cases on Wednesday , two in Waikato and the rest in Auckland.
Auckland is at Level 3, but with slightly loosened restrictions around gatherings and early childhood centres.
Northland went to Level 3 last week.
It came after Hipkins held a sudden press conference to address an unfolding situation with an "uncooperative" case who had been travelling extensively in the region after visiting from Auckland. Their travelling companion has also tested positive for Covid .
The woman was taken into police custody on Monday evening after being found at a West Auckland address.
He said the move was also required because of low vaccination rates in Northland.
A small area of Waikato went to Level 3 on September 25 after a remand prisoner and three of his household contacts tested positive for Covid-19.
It was extended on October 3.