Details of a private function in Auckland that has left 35 people with Covid-19 remains a mystery.
Health officials will only say the cluster is linked to a "private party to celebrate an event", and there are 35 confirmed and probable cases.
Director-General of Health Ashley Bloomfield today defended the lack of public information released about the Auckland party cluster, saying it was a "private event" which was "well-bounded" and everyone involved had been contacted.
The origin of the cluster is unknown, although yesterday the Director of Public Health Dr Caroline McElnay said the event was held before the lockdown.
"There is ongoing transmission happening from some of the people who were at the function ... that infection has passed within household bubbles during lockdown."
McElnay was unable to give more details, other than that the event was not linked to a workplace.
"What we are seeing with these private functions - and we see that particularly with the Bluff wedding function - is that social events, like weddings, like parties and other social events, really act as a mixing bowl for infection to be spread.
"We are seeing that in New Zealand and other parts of the world as well."
The case is being treated differently to other clusters, such as a wedding at Bluff in Southland, a St Patrick's Day party at the Redoubt Bar and Eatery in Matamata and the World Hereford Conference in Queenstown, which have been made public.
A spokeswoman for the four district health boards in Auckland today said it was not planning to add anything to the information provided by the Ministry of Health.
"We have to balance the privacy of those who are affected with public interest on a case-by-case basis.
"In this case everyone who is connected to this cluster and may have been exposed is being contacted directly by public health staff and provided with information directly through the usual public health contact tracing processes," the spokeswoman said.
The cluster is the fourth largest in New Zealand. The Bluff wedding and the Marist College cluster in Auckland are the two largest clusters, with 85 cases each. Yesterday's update showed a reduction of two for Bluff and a further case at Marist College.
The next largest cluster is the Matamata St Patrick's Day party, with 70 cases.
There are 13 clusters in New Zealand.
The Ministry of Health defines a cluster as a group pf Covid-19 cases who are linked together because they have been in the same place together.
The Herald has lodged an urgent complaint under the Official Information to the Ombudsman for details of the cluster.