NSW has reported 452 new locally acquired cases of COVID-19 and one death, with at least 54 people circulating in the community for all or part of their infectious period.
An unvaccinated woman in her 70s from western Sydney died in Westmead Hospital after the state recorded eight deaths on Monday.
Southwest and western Sydney suburbs continue to be the main generators for most of the cases, Premier Gladys Berejiklian said on Tuesday.
The isolation status of 297 cases in the 24 hours to 8pm on Monday remains under investigation.
Some 75 per cent of cases in NSW were people under 40.
Victoria has recorded 24 new locally acquired coronavirus cases on the first day of stricter lockdown measures in Melbourne.
The health department on Tuesday confirmed 21 of the new cases are linked to known outbreaks, while the remaining three are mystery infections.
Fourteen were in quarantine during their infectious period.
A case was also recorded in hotel quarantine, bringing the total number of active infections in the case to 227.
Queensland had recorded one new locally acquired case of COVID-19 as the state further boosts police defences along the border with NSW.
The local case is linked to Brisbane's Indooroopilly cluster and poses no threat, having been in home quarantine for their infectious period. There was also one other case detected in hotel quarantine.
Premier Annastacia Palaszczuk said it was another great result, on the back of zero new cases on Sunday and Monday.
"We're absolutely really happy with that," she told reporters on Tuesday.
Hundreds of close and casual contacts have been identified in the Northern Territory after a COVID-19 infected US man travelled from Sydney to the Top End.
Contact tracers have identified 63 close and 237 casual contacts after the man in his 30s flew via Canberra to Darwin on Thursday for work.
No new cases were diagnosed overnight and more virus testing facilities are set to be opened in Katherine, where the man drove on Sunday.