NSW has notched its second consecutive day with no locally acquired cases of coronavirus, in the 24 hours to 8pm on Sunday.
The results were announced by NSW Health on Monday morning.
Another seven returned travellers in hotel quarantine tested positive for COVID-19 in the latest update.
"We are concerned that other people in the broader Southern Highlands area may have unrecognised infection," a NSW Health spokesperson said.
Sewage testing has also indicated the presence of COVID-19 particles in Rouse Hill, prompting calls for people in the area to seek a swab.
The state government has also released guidelines for businesses where confirmed cases have attended, detailing their full requirements for cleaning.
Minister for Finance and Small Business Damien Tudehope said the guidelines could reduce the problems faced by businesses as the pandemic continues.
"These new guidelines are great news for businesses, as they don't need to bring in a specialist deep cleaning team, which could cost tens of thousands of dollars," he said.
Victoria also recorded no new cases on Monday, the 10th day in a row for the state.
Victorians can now move freely across the state, with the 'ring of steel' separating regional and metro areas removed at midnight last night.