One of the two positive cases in the Christchurch area is a truck driver who was working for four days during their infectious period, completing deliveries around the city, with some trips to north Canterbury.
The Ministry of Health said the two community cases were both from the same household.
In this afternoon's 1pm press conference, where it was revealed there were 89 new community cases today, Covid-19 Response Minister Chris Hipkins said the government has decided to hold the Christchurch area at its current alert level 2.
He said one of the cases recently travelled to Auckland to provide childcare. Travel to provide childcare is permitted under alert level 3 if no other appropriate person is available locally.
The person who travelled to Auckland had a negative test before travelling north and a second negative test before returning to Christchurch on Friday, 15 October.
The other case works as a truck driver and the company the person works for is assisting with tracking their whereabouts during the four days the person was working during their infectious period. Initial information indicates the person was completing deliveries around the Christchurch area, with some trips to north Canterbury.
Both people became unwell last week, were tested on 26 October and both returned positive test results last night. Currently there are three households where nine close contacts have been identified.
Both cases are currently isolating safety at home, with public health oversight, and with plans underway to transfer them to a local quarantine facility.
The local public health unit is gathering further information from the cases to identify close contacts and exposure events, including any locations of interest.
People across Canterbury are urged to closely monitor the ministry's locations of interest webpage, which is updated regularly.
In addition, people in Canterbury - especially those who live in Christchurch - with any symptoms, no matter how mild, are asked to please get tested, even if they are vaccinated. Unvaccinated people are urged to get vaccinated.
Testing and vaccination sites are available throughout Christchurch. Please see the Healthpoint website for locations.
Wastewater samples taken in Christchurch on Tuesday and Covid-19 was not detected. ESR is collecting further samples from Waimakariri, covering Rangiora, Kiapoi and Woodend, and Ashburton, in addition to further testing in Christchurch.
Hipkins said the government was looking at whether there should be vaccination requirements for people travelling on flights inter-regionally.
Earlier today, Hipkins said the two cases in Christchurch are not vaccinated, and their use of the Covid-19 Tracer app has been low.
Hipkins told Morning Report "The nature of their contacts in Christchurch will be established during the morning and then we'll have a bit more information to share, but you know, these cases came in quite late last night.
"My understanding is that they've been unwell for a while so they could have been symptomatic and infectious for a period of time whilst back in Christchurch and so that's one of the things that the contact tracers will be working on as a as a top priority this morning - to identify exactly what the nature of the potential exposure in Christchurch is."
"As of last night that identified one other household so far that the person had had contact with ... but we'll know more within the next few hours, hopefully."
The impact of their low use of the Covid Tracer app "ultimately would depend on exactly how much they've been out in the community, you know if they've been unwell, they may well have been staying at home for much of that period of time.
"If they have had a significant amount of movement within the community, and then the fact that they haven't kept records does make that more challenging because human nature is everybody will forget things."
The pair seemed to be co-operating with authorities so far, he said.
According to Canterbury DHB figures, 89 percent of people in the region have received their first dose and 68 percent are fully vaccinated.
Hipkins said that was good.
"Once you get up to those sorts of rates, that does start to have an impact on the spread of the virus."
But the cases illustrated why there were still restrictions in the South Island, he said.
Christchurch Mayor Lianne Dalziel said the two Delta cases were the wake-up call her city was dreading.
Dalziel told Morning Report it was disappointing the pair were not scanning QR codes and were unvaccinated.
Seeing the damage one case caused in Auckland, people needed to be extremely vigilant, she said.
She wanted tougher border requirements for people leaving locked down regions.
Christchurch-based National Party MP Gerry Brownlee backed a move to a lockdown - if it was the only way to contain a widespread outbreak.
"What we've got now is the reality of possibly greater restriction that we've enjoyed for a long time and I hope that the Ministry (of Health) in their consideration is sensible, and that the people of Christchurch … continue to use the QR codes, wear masks and where appropriate, (socially) distance," he told Morning Report.
However, before a lockdown decision was made he would want more information about the movements of the pair.
"I think you've gotta be pretty sensible about whether you decide that the whole province or the whole city needs to lock itself down - or just rely on the fact that we have increasing vaccination rates... I just really hope that there is a sensible analysis of what the risks are."
Epidemiologist professor Michael Baker said the new Christchurch cases were expected but nonetheless concerning.
"Some people felt there was some inevitability about this virus in this outbreak, spreading all around the country, including the South Island.
"We've already seen how easy it is for a case to a travel from the North Island to Blenheim recently, so this is probably expected but obviously quite a shock.
"If there's only one case in one household member, contact tracing should work very well. The bigger issue is how many other cases are incubating in the South Island given we have very few controls on infected people getting on flights at the moment.
"One of the problems, of course, is that a high proportion of people will be asymptomatic or have only a few symptoms, the occasional person will also be vaccinated now, so it is quite tough to pick up all of these outbreaks very early, so it's just critical for people to come forward if they've got any symptoms at all.
"I think if the outbreak is well defined - so it's just the person who's travelled to Christchurch and their household members - that should be very manageable with contact tracing and the usual methods.
"I think there wouldn't be a need to raise alert levels in Christchurch if the contact tracing puts a really good boundary around it.
"The risk assessment they're doing now will be very thorough I'm sure, and that will give us an idea for this case. I think the wider question is how many other cases now are incubating the South Island."
There were "a whole lot of precautions" that could be used to keep the virus out of the South Island, Baker said.
"The first thing is limiting numbers of people travelling to the South Island from infected areas to just essential workers, for example.
"The other thing is at least some basic screening before people go on flights particularly whether they've come from an area that's under level 3 restrictions where there is considerable transmission and potentially there should be a requirement for pre-travel testing, I think increasingly there should be a requirement for vaccination."