There is one new case of Covid-19 in New Zealand managed isolation, with none in the community.

The Ministry of Health said its officials were in close contact with counterparts in Victoria following the state's seven-day lockdown announced today.

It was "crucial" that any Kiwi travellers in Victoria since May 11 were checking Victoria Health's locations of interest.

There were 34 positive cases in Melbourne as at 1pm today with 150 exposure sites across the city.

Director-general of health Dr Ashley Bloomfield said it was "critically important" people record their movements and scanned QR codes in the event that positive cases were found in New Zealand.

Anyone who had been at a location of interest at the specified time must immediately self-isolate and call Healthline on 0800 358 5453.

Anyone with symptoms who had been in the wider Melbourne area since May 11 should also ring Healthline and arrange a test. People who had been in the Whittlesea local government area since May 11 should also ring Healthline.

If you have been in Melbourne

Authorities in Melbourne and wider Victoria are poised to announce further restrictions this afternoon after the state's cluster grew to 26 cases.

As a result, speculation is mounting that a lockdown is about to be announced. But exactly how long that will be is yet to be revealed.

If a lockdown does go ahead, it will be the fourth time people in Melbourne will have experienced one due to Covid.

Because the first case in the Melbourne cluster was identified just over two weeks ago - on May 11 - it is possible that people from the Whittlesea local government area in Melbourne may have been exposed to the virus and are now in New Zealand, the Ministry of Health said.

"The ministry is asking anyone who has been in that area to have a test five days after they were last in Whittlesea and stay in their accommodation until they have a negative test result - even if they do no have symptoms."

Anyone from the wider Melbourne region who develops symptoms while in New Zealand is also urged to take action immediately by calling Healthline on 0800 358 5453 and arrange to get a Covid test.

The locations of interest connected to the Melbourne cluster are regularly updated on Victoria's dedicated Covid website.