Queensland has recorded two new local cases of COVID-19, according to Queensland health authorities.
The first case involves a woman who travelled from Melbourne and was identified by health authorities on Wednesday.
The second case is her husband, who has now also tested positive.
Queensland's Health Minister Yvette D'Ath said the husband travelled from Victoria to Queensland via regional New South Wales.
Authorities in NSW are now concerned there is a "serious risk" of a COVID-19 outbreak in the state.
"I am very concerned that we've had people leave the lockdown and travel across our state and into Queensland, putting everyone at risk," NSW Health Minister Brad Hazzard said, according to the Sydney Morning Herald.
"What we need to understand is why that was done and there's no clarity on that at this point."
D'Ath said investigations were continuing into why the couple left Melbourne while Victoria was in lockdown but said she would be waiting for all the facts to come to light before making any comments on the couple's journey.
"I don't want to jump to conclusions before we have all the facts, specifically if they had a travel declaration.
"The husband was here with a new job, and we know that is one of the grounds that people can travel, but I don't have the details so I’m not going to judge anyone’s behaviour until I know all the facts."
The husband travelled through NSW while potentially infectious from June 1 to June 5.
"The case drove from Melbourne to the Sunshine Coast in Queensland, stopping at places in Gillenbah, Forbes, Dubbo and Moree," NSW health authorities said.
So far 17 close contacts of the couple have been identified, with three of those testing negative.
The new community cases in Queensland come as Melbourne prepares to come out of lockdown at 11:59pm on Thursday.
A number of restrictions will remain in place though, with residents prohibited from travelling more than 25km from their homes.
There will also be a limit on the number of people allowed to attend events such as weddings, funerals and religious ceremonies. And while cafes and restaurants will be allowed to open, they will only be permitted to have a maximum of 50 people inside.
Despite the fact the city is still in lockdown on Thursday and the travel bubble with Victoria on pause, a limited number of "green" flights arrived at Auckland Airport last night and today carrying Kiwis who were stuck in the state after flights were suspended on May 25.
Four new communitiy cases of COVID-19 were recorded in Victoria on Thursday.