NSW Health is urgently contacting members of a sporting club in the state's western Riverina region who attended an event in Victoria and may have come into contact with a confirmed case of COVID-19.
The club members from Tooleybuc attended a sporting event in Cohuna, Victoria on Saturday, May 22 from 12pm to 5pm.
Anyone who attended is asked to immediately self-isolate and await further advice from NSW Health.
In a statement on Wednesday night NSW Health said it was working to set up increased virus testing capacity in the Tooleybuc area.
The NSW government is advising people against travelling to Melbourne and Bendigo for the time being as Victoria deals with a fresh COVID-19 outbreak.
A COVID-19 cluster in Melbourne's north has almost doubled to 15 infections after six extra cases were confirmed on Wednesday.
"Unless you absolutely have to go down there, just consider your options," NSW Premier Gladys Berejiklian said on Wednesday.
Genomic sequencing shows the outbreak is linked to a Wollert man who contracted COVID-19 in South Australian quarantine earlier this month.
The man, in his 60s, could be the possible 'source case' for the City of Whittlesea outbreak, although a definitive link is yet to be established.
Chief Health Officer Kerry Chant says those who have returned from Melbourne since May 12 should keep a close eye on the Victorian government's growing list of COVID-19 exposure sites.
They should also avoid aged care or healthcare facilities.
Anyone in NSW with respiratory symptoms should get COVID tested.
At least two people in NSW who visited sites on Victoria Health's exposure list had tested negative to the virus, Dr Chant said.
The two people will quarantine for 14 days from their exposure date.
Ms Berejiklian said the Victorian COVID cases were a reminder of the importance of getting vaccinated.
"We're still in a very initial stage of getting our population vaccinated and that's why it's essential ... when you look around the world, look at what's happening in Victoria, that could happen in any state in Australia," she said.
"We do not have enough of our population vaccinated.
"We have greater choices for our population when the vast majority is vaccinated - that gives us freedom to make decisions."
More than 1.1 million vaccinations have been administered in NSW, including jabs overseen by the Commonwealth.
There were no locally acquired COVID-19 cases in NSW in the 24 hours to 8pm on Tuesday, with two cases in returned travellers in hotel quarantine.
NSW Health doled out a record 13,200 vaccines in the same 24-hour period.
The Victorian government has not yet ruled out a snap lockdown.