Two managed isolation hotels in Auckland will stop accommodating returnees until further notice to review contamination within the facilities.
A joint Ministry of Health and MIQ advisory group has recommended stopping the arrival of any further returnees into the Grand Mercure and Grand Millennium to investigate, the outcome of which is expected to be at the end of April.
The group has also recommended all returnees currently at the Grand Mercure be tested at day seven of their stay, in addition to other testing.
It comes after three workers at the Grand Millennium recently tested positive for COVID-19 - a cleaner known as Case A, a security guard known as Case B and a close contact of his, Case C.
Last week it was revealed Case B hadn't been tested since November, when he should have been tested fortnightly. An investigation is underway into whether he lied to his employer about his testing record.
It also follows genome sequencing showing a link between two returnees at the Grand Mercure, despite the two arriving on different flights and staying in separate rooms on different floors of the facility.
Head of MIQ, Brigadier Jim Bliss, said returnees currently in the facilities will continue with their isolation and leave after their 14-day stay.
There are currently 83 returnees at the Grand Millennium, all of whom will have exited on Wednesday. The 141 returnees currently in the Grand Mercure will be required to have a day seven test and will all have exited by next Tuesday.
Pausing arrivals at the facilities will allow contractors full access to both facilities to investigate potential sources of transmission - including aerosol transmission, however unlikely it is.
"The risk presented by ventilation systems has always been assessed by health experts as very low and the overall risks to returnees and staff of contracting COVID-19 within MIQ facilities has been and remains extremely low," said Brigadier Bliss.
"Nevertheless, we have made investments in our facilities to address the risk that the ventilation systems may be presenting with regards to transmission of COVID-19."
He said that's why day one testing was introduced in MIQ in January as well as pre-departure testing.
"Attention to infection, prevention and control procedures and protocols regarding returnee movements, vaccination of MIQ staff and regular testing provide additional safeguards to reduce transmission should there be a case identified within an MIQ facility," he said.
"New Zealand has a model of acting cautiously, a model which has worked well for us as a country and has enabled us to enjoy unprecedented freedoms in the midst of this global pandemic."