NZ’s health ministry discovered the cases on Wednesday night, a development Christchurch Mayor Lianne Dalziel labelled “the wake-up call we’ve all been dreading”.

The cases are both from the same household, and the link to NZ’s Delta outbreak is believed to be recent travel from one of the cases from Auckland.

COVID-19 Minister Chris Hipkins told TVNZ both cases were unvaccinated, and the government was yet to rule out a snap lockdown.

“They’d been back in Christchurch for several days, potentially up to a week,” Hipkins told Radio NZ.

“This is someone who did have a negative test prior to travel … my understanding is that they’d been unwell for a while.

“Given there are a number of days when the person was infectious, It’s quite possible there will be more (close contacts to test).”

Hipkins said the pair did not use QR codes to sign in on their whereabouts, but were co-operating with contact tracers who continue interviews on Thursday morning.

Dalziel said it was “extremely disappointing” the pair weren’t signing in, as is mandatory in NZ.

“This has been the wake up call we’ve all been dreading and a reminder of the importance of being absolutely vigilant,” she told Radio NZ.

According to the Canterbury district health board, 89 per cent of eligible locals are partially vaccinated and 68 per cent are double-dosed.

Dalziel said she wanted Christchurch to avoid lockdown.

“I’m hoping they haven’t been out and about. I’m hoping that this isn’t as widespread as (the Auckland outbreak) became,” she said.

The government is expected to reveal more, including a possible snap lockdown, at 1pm.

A single case was picked up on South Island earlier this week, but the case found in Blenheim has not yet resulted in further spread.

Christchurch has enjoyed a run of almost a year without COVID-19.

The last confirmed community case in the Garden City was in November, and the last confirmed community transmission was in May last year.