Covid-19 on a rubbish bin at a Christchurch managed isolation facility likely led to two people contracting Covid-19, according to the Ministry of Health.
Director of Public Health Dr Caroline McElnay gave an update on the cases during this afternoon's 1pm press conference.
McElnay said the first case - a person who had arrived from India on August 27 - was reported on September 19 as having completed 14 days in managed isolation in a facility in Christchurch and had returned two negative tests.
She said that person then flew, along with others from the managed isolation facility, on a charter flight from Christchurch to Auckland on September 11.
"While we cannot be conclusive, we believe this person was likely infected on the charter flight by a person seated behind them, who had also completed 14 days of managed isolation and returned two negative tests.
"That person did not have any symptoms but tested positive for Covid-19 on September 23."
McElnay said investigations at the managed isolation facility showed that the second case - the one reported on September 23 - was likely exposed to Covid-19 near the end of their stay in quarantine and was likely incubating the virus at the time of their day 12 test, which was negative.
The Director of Public Health said public health officials and staff at the Christchurch facility conducted an "extensive investigation" into where the virus could have come from and, after using CCTV, they believe they've found the source.
"While we cannot be certain, our hypothesis is that the virus may have been transmitted to [the second case] via the surface of a rubbish bin which was used by another returnee who was likely infectious at the facility.
"This returnee tested positive on day 12 of their stay in managed isolation, however they were likely infectious a few days before testing positive."
As a result of this, the Ministry of Health has now updated its guidelines at facilities so that all bins in public areas will now be no-touch and all rubbish must be securely sealed in plastic bags prior to disposal in the bins.
No other cases were reported from the flight itself but household contacts of the two confirmed cases did contract Covid-19.