There are no new cases of Covid-19 to report in the community or in managed isolation, according to the Ministry of Health.

The Ministry also said that following last night's announcement that New Zealand is pausing Quarantine Free Travel with Victoria until Friday 4 June, the Ministry's contact tracing team emailed around 5,000 people who had travelled from Melbourne between May 20-25.

The email instructed them to get a test and self-isolate at home or in the accommodation they are staying in until they have a negative result. It also instructed them to contact Healthline if they need further advice or to report if they had been at a location of interest.

Roughly 500 of those 5000 people were unable to be reached by email and are being followed up with phone calls and texts.

This follows contact tracers previously contacting everyone who returned to New Zealand from Melbourne since 11 May and providing advice on checking locations of interest and other actions required, according to the Ministry's statement this afternoon.

"The Director-General of Health Ashley Bloomfield is now requiring everyone who has visited the Greater Melbourne area since May 20 to isolate at their place of residence until they receive a negative COVID-19 test result.

"This is an additional precaution. The number of locations of interest around Melbourne has grown substantially, making it difficult for visitors to easily keep track."

Yesterday, Acting Victoria Premier James Merlino put the state in a seven-day "circuit breaker" lockdown in response to the new active cases in Melbourne.

There 30 positive community Covid cases in Melbourne – four new confirmed overnight.

That number, however, is expected to increase given there were 150 exposure sites across the city and more than 10,000 contacts identified.

Merlino will provide another update later today.

Yesterday, Covid-19 Response Minister Chris Hipkins – along with director general of Health Ashley Bloomfield – announced that New Zealand's travel bubble with Victoria will be paused for another seven days.

That means people will not be able to travel between the two locations without need to quarantine until at least 7.58pm on Friday, June 4.

Anybody who had been in one of the locations of interest in Victoria couldn't travel to NZ for at least 14 days after they had been at the location, Hipkins said.

People who had visited one of those locations could not travel to New Zealand even if they had a negative Covid-19 test, Hipkins said.

Further restrictions, such as pre-departure testing, were being considered, he said.

Anyone who has travelled to NZ after being in the greater Melbourne area since the 20th was now required to be tested and to isolate, Bloomfield said. That's in addition to those who travelled to NZ since May 11.

About 5000 travellers are affected by the new restriction.

The Ministry of Health will likely provide more details in its statement this afternoon.

Yesterday, Merlino said that the state has never experienced an outbreak of a strain that spreads this easily, saying the time between catching the virus and passing it on "is tighter than ever".

"Our contact tracers are identifying and locking down the first ring, second ring, and third ring within 24 hours. They have never done that before.

"That's the fastest our contact tracers have ever moved within a 24-hour period, identifying and locking down first, second, and third rings of cases. But despite working as fast as this, and my thanks to all of our contact tracers, this variant is moving faster still."