Ministry of Health deputy director of public health Dr Harriette Carr said the investigation concluded there were no bubble breaches.
"But it found that the three cases were genomically linked to a person in the room opposite, and not to the pre-existing case within their bubble of four people.
"They found doors to rooms on opposite sides of the corridor were opened at the same time for about 3-5 seconds on four occasions between July 19 and 27, when a case in the room opposite would have been considered infectious," Carr said.
"The proximity in time and location when doors were open, and likely sharing of air that may have occurred, is considered the most likely explanation for this transmission."
After viewing security footage it found the solo traveller did not leave their room but doors on appositive sides of the corridor were opened at the same time for 3-5 seconds on four occasions between July 19 and 27 when the solo case would have been considered infectious. Three of the occasions were due to regular meal deliveries and one was a health check.
It was confirmed no other returning travellers would have been exposed and staff were wearing appropriate PPE at the time.
"We're confident there was no risk to the public as a result of this," she said.
King, said as a result of this investigation, there had been immediate changes at Jet Park.
"This is the first time we have seen something like this occur at the Jet Park quarantine facility.
"As such, we've made immediate changes to meal delivery and health check procedures to help prevent future episodes of doors opening at the same time. There are low numbers in Jet Park currently so we've also been able to separate returnees more widely throughout the facility as much as practicable," King said.
"There are elements of human behaviour here which are difficult to completely control.
The ministry's Carr said: "We're not able to control the exact timing of returnees opening their doors – but we've put measures in place to help reduce the chances as much as is practical."
Changes would extend to every managed isolation facility in the country.
"The MIQ Technical Advisory Group has considered this investigation and is working on recommendations to reduce the number of occurrences of door opening and, where possible, eliminate synchronous door opening across all 31 facilities," she said.
"While I have no reason to believe they weren't, I've also commissioned an operational assessment of the situation to determine whether the relevant Standard Operating
"Procedures and processes were followed and if any changes should be made as a result of this situation. All of this advice will be considered together and I will provide a further update on the final course of action once it is agreed."
