Victoria had no locally acquired coronavirus cases to report on Friday, on day one of Melbourne’s return to a post-lockdown life.

It is the first day since mid-May, when Victoria’s latest outbreaks began to emerge, that there have been no community cases anywhere in the state.

It follows a worrying development on Thursday, with confirmation that four members of a Melbourne family with no known links to current outbreaks had tested positive for the virus.

However – even as Melburnians indulge in freedoms such as being able to leave their homes whenever they like – there remain significant concerns for the spread of the virus in the city.

Tweet from @VicGovDH

Late on Thursday, Victorian health officials had also started interviewing a couple who left outer-suburban Melbourne during its extended lockdown. They drove through NSW to Queensland and tested positive for the virus while staying with the woman’s parents on the Sunshine Coast, sparking health alerts in three states.

Also on Thursday, there were wastewater detections of the virus reported in the suburban Pascoe Vale, Scoresby and Vermont areas.

Anyone with respiratory symptoms in those areas is urged to get tested.

And six more public exposure sites were added for Bundoora, Heidelberg and Thomastown in Melbourne, dating from May 28 to June 7.

They include the Coles-Warringal Shopping Centre in Heidelberg, the Coles at Bundoora Square, the McDonald’s drive-through at Thomastown and Gami Chicken & Beer at Epping.

• See an updated list of exposure sites here

While the city’s easing of restrictions went ahead at midnight on Thursday as planned, Melburnians must continue to wear masks whenever they leave their homes.

Melburnians are also restricted to a 25-kilometre travel limit from home.

Virus rules have also been further relaxed in regional Victoria.

Initially, masks were no longer going to be compulsory outdoors when the Melbourne lockdown lifted, as long as social distancing was maintained.

That changed with the revelation of Thursday’s four new cases, from a single Reservoir household in the city’s north.

Deputy chief health officer Allen Cheng said the family were not close contacts of previous cases and hadn’t visited any listed exposure sites, although they live close to the City of Whittlesea outbreak.

“These new cases are really the strongest reminder that we are by no means out of the woods yet,” Professor Cheng said.

Authorities are still awaiting genomic testing to see if the family has the Delta or Kappa strain of the virus.

Their close contacts are self-isolating and some have already returned negative tests.

Meanwhile, the couple who drove to Queensland remain under investigation and it is unclear how they caught the virus.

The woman and her husband left Melton, in Melbourne’s outer west, on June 1, reportedly so he could start a new job on the Sunshine Coast. She was the first to test positive on Wednesday, followed by him on Thursday, after their road trip through regional NSW and into Queensland.

However, Queensland health authorities are confident the couple are at the end of their infection period.

They say the couple did not apply for a travel exemption to enter the state.

Testing has been boosted in regional NSW and Queensland following the couple’s diagnoses. So far, NSW has reported no new community cases and Queensland has only the former Melbourne couple.

Victoria had 78 active cases on Thursday, down five from Wednesday.

-with AAP