There are three new cases of Covid-19 in MIQ and none in the community.

The good news comes after a number of investigations were launched over Covid-19 transmission between returning Kiwis at a second Auckland managed isolation hotel.

Director general of health Dr Ashley Bloomfield said how the Grand Millennium cleaner, known as case A, contracted covid was still under investigation. The household's contact who initially gave a weak positive has given a second negative covid test.

All close contacts of the cleaner had also returned negative tests.

Yesterday it was revealed the Grand Mercure in downtown Auckland was under investigation after a possibility of a transmission within the facility with hundreds of people who had completed managed isolation in the past 10 days asked to get re-tested and self-isolate.

Bloomfield said efforts were underway to contact the 250 people that had left since March 10, while 190 people had been contacted as of 9am today.

Fourteen people had had their time in managed isolation extended for a further 14 days.

Gead of Managed Isolation and Quarantine Brigadier Jim Bliss said an investigation was now being launched at the Grand Mercure and into off-site exercise yards. He said a person who was positive was on one such exercise outing. The busing journeys to the off-site exercise field had now been paused, Bliss said.

One of those infected travelled on a bus to an exercise field with others from different facilities.

Officials were probing the source of the infection.

Meanwhile, some 5000 vaccination doses were expected to be administered across the North Island this weekend including at hotels and doctors clinics.

There had now been around 50,000 doses given across the country, Bloomfield said.

Earlier in the year three people in managed isolation at Auckland's Pullman Hotel caught Covid-19 in three separate incidents.

The hotel was temporarily closed for decontamination and upgrades after three returnees fell ill after completing their mandatory 14-day stay in isolation, sparking fears the infection may have spread across the community.

At the time, Bliss confirmed genome sequencing confirmed all three cases had the variant first identified in South Africa.

A report into the episode in February indicated poor ventilation in the hotel's corridors contributed to the spread.

The Ministry of Business, Innovation and Employment was also conducting an internal investigation into the bus journeys taken by returnees to determine what happened in this case and what improvements could be made to strengthen their processes.