The first case returned a negative test before coming to the South Island but later became unwell.
Covid-19 Response Minister Chris Hipkins said both are unvaccinated and had "not been particularly good users of the Covid tracer app".
Thirteen locations of interest have been announced so far and while none have been confirmed today there is more information expected later this afternoon.
After the positive cases were confirmed, testing sites were swamped by people with queues of hundreds of cars across the city.
"Yesterday, more than 3000 Covid-19 swabs were carried out at our testing sites and via general practice teams across the Canterbury community," said Dr Helen Skinner, the senior responsible officer for the Canterbury District Health Board's Covid-19 response.
"This excludes those taken in Managed Isolation and Quarantine facilities.
"There high demand for Covid-19 testing in Canterbury currently which is encouraging."
Skinner said to cope with the demand the DHB had increased staff capacity at testing centres.
"Operating hours at our testing centres are also being extended where possible, with Orchard Road staying open late last night," she said.
"It's important to note that testing is also available across general practice teams, with some having significant capacity currently.
"Cantabrians who are experiencing any Covid-19 symptoms or have visited a location of interest are urged to get tested."
The first thirteen locations confirmed yesterday are:
• The Mad Dairy on Main South Rd, Hornby: 12.45pm to 1.15pm, October 18
• Hornby Chinese Takeaways on Main South Rd, Hornby: 12.45pm to 1.30pm, October 18
• Burger King on Curletts Rd, Sockburn: 4.30pm to 5.30pm, October 18
• Z Curletts Rd on Curletts Rd, Sockburn: 5pm to 5.30pm, October 18
• Supervalue Fendalton Village on Ilam Rd, Bryndwr: 6.45pm to 7.45pm, October 18
• Try's Bakery on Main South Rd, Islington: 7.30am to 8.30am, October 20
• Caltex on Blenheim Rd, Riccarton: 5.45pm to 6.15pm, October 20
• Gloucester and Stanmore Corner Dairy on Stanmore Rd, Linwood: 6pm to 6.30pm, October 20
• Pannell Discounter on Wainoni Rd, Wainoni: 1pm to 1.45pm, October 2
• Waimairi Takeaway on Greers Rd, Bryndwr: 4.15pm to 5.15pm, October 23
• Kims Corner Dairy on Greers Rd, Bryndwr: 4.30pm to 5.15pm, October 23
• New World in Bishopdale Court, Bishopdale: 11.30am to 12.30pm, October 25
• Kens Takeways on Sawyers Arms Rd, Bishopdale: 4pm to 5pm, October 27
It is not yet known if there are any further cases of Covid-19 in the Christchurch region.
Further information on case numbers and any change to alert levels for the area will be released at 1pm in an email statement from the Ministry of Health.
People across the Canterbury region are being urged to get tested if they are sick or have any of the symptoms of Covid-19.
Vaccination is also being heavily encouraged as authorities battle to reduce the spread and damage caused by the deadly Delta variant of the virus.
People can be tested at their general practice - but must call before turning up for a test.
Community-based testing centres are also available where people can drive up or walk in.
Testing is free, unless you require a test for travel overseas.
The Covid-19 CBTCs currently operating in Canterbury are:
• Orchard Rd CBTC (near Airport), 174 Orchard Road, (Off Harewood Road), Christchurch. Open 9am-late, 7 days a week.
• Whānau Ora Community Clinic CBTC (Wainoni), 250 Pages Rd, Wainoni, Christchurch. Open 9am-3:30pm (or later if demand requires), 7 days a week.
• Ashburton Hospital site CBTC - 28 Elizabeth St, Ashburton hospital site, Open 10am-2pm, Tuesday to Thursday and on Saturday (Walk-in/no referral required)
Yesterday the Canterbury District Health Board said its testing centres were already experiencing increased demand.
"And we have increased capacity to respond to this, with additional staff brought on board," said CDHB senior responsible officer for Covid-19 response Dr Helen Skinner.
"Our Orchard Road site will remain open late today as demand requires.
"Please get tested if you visited a location of interest or have cold and flu symptoms."
Full details of testing options in Canterbury can be found here: https://www.cdhb.health.nz/your-health/canterbury-dhb-covid-19-information/#4
