Updated 4.45pm: Prime Minister Jacinda Ardern and Director-General of Health Dr Ashley Bloomfield have announced all of New Zealand will remain at Alert Level 4 until 11.59pm Friday August 27. 

Auckland will remain at Alert Level four until 11.59 Tuesday August 31.

The nation-wide alert level will be reviewed on Friday, while Auckland’s alert level will be reviewed on Tuesday. 

“The safest option for all of us right now is to hold the course for longer,” prime minister Jacinda Ardern said in a media briefing this afternoon (August 23).

A "heat map" of close contacts of confirmed identified more than 100 people located on the South Island, including sights such as Queenstown and Wanaka. However no contacts on the South Island have returned a positive test so far. 

Jacinda says while the number of cases has increased and the number of close contacts who have spread throughout the country means a high degree of uncertainty. 

Early estimates of this outbreak suggest one person can spread the virus to six or higher, she says. 

Over 13,000 close contacts are currently recorded - the highest than any other outbreak in New Zealand since the Covid-19 pandemic began. 

The head-start the Delta variant had means it already has a far-reach. She says this has justified the lockdown and nation-wide move to Alert Level 4. 

Jacinda warned the numbers of cases may get worse before they get better. 

"We don't think we have reached the peak for this outbreak, or the edges of it," Jacinda says. 

Seven people are in hospital with Covid-19.