Victoria has reopened to regional NSW, with the introduction of a new "traffic light" system for interstate travel.
Permits designating regions in other parts of Australia green, orange or red zones depending on coronavirus risk were to go live from 6pm Monday.
Regional NSW will be classified orange.
Greater Sydney and Greater Brisbane remain red, although Premier Daniel Andrews says the classifications could change "late in the week".
"Whilst the restrictions that have been imposed in Greater Brisbane come off at 6pm tonight, the public health team is still not 100 per cent confident that we could have people from Brisbane returning to Victoria," he said.
"There are still many close contacts that have not been tested. That's a relatively new outbreak."
Mr Andrews conceded it was a "deeply inconvenient and challenging time" for Victorians stranded interstate, but insisted he had to follow public health advice.
"The stakes are very high here," he said.
He said Victorians planning interstate travel need to be aware to the possibility their plans could change.
"That has got to be part of your thinking because this is not normal," he said.
"We are in a global pandemic. There is no vaccine (in Australia) yet."
Opposition Leader Michael O'Brien labelled the permit requirement for returning from green zone areas a "massive overreach".
"It puts the government in control of every single Victorians' life," he told reporters.
Anyone wanting to come to Victoria from regional NSW will need to apply for a permit via the Services Victoria website.
A $4,957 fine will apply for arriving without one and police will continue to patrol the Victoria-NSW border.
Monday marked the fifth consecutive day the state recorded no new local or interstate COVID-19 cases, though a returned traveller in hotel quarantine tested positive.
It brought the state's active case total to 40.
A Victorian child who tested positive after travelling overseas will not be included in the tally, having returned the result after arriving in Israel on 9 January.
The child attended Armadale's Explorers Early Learning Centre, 8km southeast of Melbourne, on 7 January.
A Department of Health and Human Services spokesman told AAP they were working with colleagues in Israel to confirm the test result.
Cleaning and contact tracing is underway but Victoria's Chief Health Officer Brett Sutton suspects the case is a false positive.
"Children are extremely low risk of having serious illness," he said.
"They can become infected but transmissibility in childcare settings is pretty low."
The test was a rapid test, which has been proven to be less accurate than a nose and throat swab.
"These rapid point-of-care tests are very useful but they can turn up a positive result in somebody (who is) not truly a case," Prof Sutton said.
About 18,660 people were tested in Victoria on Sunday.
How does Victoria's new traffic light system work?
Red zone: If you have visited a red zone in the past 14 days, you will not be allowed to enter Victoria without an exception or exemption. If you try, you will be fined $4,957 and turned away. Greater Brisbane and Greater Sydney remain red zones.
Orange zone: If you have visited an orange zone, you can apply for a permit and need to take a coronavirus test within 72 hours after arriving in Victoria, isolating before and after, until you receive a negative result. From 6pm on Monday, Regional NSW will become an orange zone.
Green zone: A green zone means you can apply for a permit and enter Victoria.
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