• Victoria reports 331 new COVID-19 cases, 19 deaths
• NSW reports biggest one-day rise in cases since April

SYDNEY: Australia's second-most populous state reported only a small rise in new COVID-19 infections on Tuesday, boosting hopes that case numbers are stabilising after a second wave forced authorities to put the city of Melbourne back into lockdown.

Victoria state, which currently accounts for nearly all of Australia's new cases, detected 331 COVID-19 infections and 19 deaths in the past 24 hours, up from 322 infections and the same number of fatalities a day earlier, health officials said.

Daily infections in Victoria peaked at 725 on Aug. 5 and have been trending lower in recent days, following the imposition of a hard lockdown in Melbourne on July 19.

While the lockdown has caused significant economic harm, authorities said the restrictions that will run until September are bearing fruit.

"We continue to see numbers coming down. Exactly how long that takes and to what the lowest number is we can get to, only time will tell," Victoria state Premier Daniel Andrews told reporters in Melbourne.

"There is no alternative, there is no choice."

Nationally, Australia has detected about 22,000 infections and 332 deaths from COVID-19, far fewer than many other developed nations.

Still, the country was recording less than 20 new cases a day as recently as June. Quarantine breaches in Victoria are believed to believed to be the source of the latest outbreak.

Officials have begun an inquiry, with Andrews on Tuesday called as a witness to explain why the state government chose to employ private security in hotels used to quarantine people returning to Australia from overseas.

Outside the two largest states of Victoria and New South Wales, the virus has effectively been eliminated.

Worrying health officials, New South Wales on Tuesday reported 22 new COVID-19 cases, the biggest one-day rise since April 17.

About a third of the new cases were from a cluster at a school in Sydney's northwest, with authorities still unable to trace the original source of the outbreak.

"It's not always possible to determine the source and that's what worries us most," said state health minister Brad Hazzard.