New Zealand's COVID-19 Response Minister Chris Hipkins said the "travel bubble" with Victoria has been suspended for three days from Tuesday evening.
Those who have attended a close contact location must contact ACT Health, get tested for COVID-19 and quarantine for 14 days even if they have a negative test result.
Earlier: New exposure sites in Epping, Bundoora, Maribyrnong and Reservoir have been identified following four confirmed COVID-19 cases in the City of Whittlesea.
Professor Sutton confirmed the COVID-19 variant in the Whittlesea outbreak is B1617, which was first identified in India in October a year ago.
Dr Bennett said we are in an ongoing "risk" where we can not become complacent as there are no guarantees.
Schools and workplaces remain open and Victorians who live in greater Melbourne can still travel to regional Victoria.More news: European Union to cut air links with Belarus following flight diversion incident
Five new locally acquired cases were reported in Victoria on Tuesday, a day after four infections were recorded in Melbourne.
"Further, staff returning from Greater Melbourne who provide home-based aged care and disability services that involve close physical contact with clients, should exclude themselves from providing in-home care for a period of 14 days since they were last in the area".
The outbreak grew to five on Tuesday morning with a man in his 60s also testing positive. Contact tracing of the new cases is underway.
The health department said if you have any symptoms of COVID-19 - such as fever, cough, sore throat, runny nose, chills or sweats, or change in sense of smell or taste - get a test immediately.
"I am concerned about the people that were on a crowded train on the Craigieburn line in the Wollert case", chief health officer Brett Sutton said on Tuesday.
Genome sequencing has shown the cases are closely linked with a previous case in Melbourne reported on May 11. At the press conference, officials said that it was possible there was a "missing link".More news: Italian cable auto crash kills nine, injures two children
"This virus is bad in the way that it can spread", Chief Health Officer Brett Sutton told ABC Radio Melbourne on Tuesday.
He told 3AW on Tuesday afternoon cases in the Whittlesea outbreak had not been linked to an exposure site blunder where the government said the Wollert case visited Epping Woolworths while infectious rather than Epping North.
Thousands have been ordered to self isolate and undergo Covid-19 tests with health alerts issued for several sites, including one of the largest shopping centres in the country.
Prime Minister Jacinda Ardern said today that New Zealand health officials were "in close contact" with their counterparts across the Tasman, as the state of Victoria imposes new restrictions.
Under new restrictions face masks must be worn indoors unless there's an exemption in place.
The ministry also recommends that anyone in New Zealand who has visited Melbourne since May 11 should monitor for symptoms and if any develop, seek advice on testing from Healthline.More news: COVID-19: downward trends continue as Alberta starts May long weekend