A second hotel quarantine worker has tested positive for COVID-19 in Melbourne, days after another worker .
Victorian health authorities announced the new case at midnight after the woman, who worked as an authorised officer at Melbourne Airport's Holiday Inn, returned a positive test after developing symptoms on Sunday.
She had earlier returned a negative test at the end of her shift on Thursday.
The woman was tasked with issuing detention notices to international arrivals as they enter the hotel or are moved to another facility.
No further positive cases had been detected as of Monday morning, out of more than 11,300 tests on Sunday.
Victoria Police Minister Lisa Neville told reporters on Monday that there was no evidence of a breach in infection control protocols.
"We will need to wait for genomics," she said. "Obviously we are also checking rosters and checking her movement through the hotel, whether there was any engagement with anyone who was positive.".
Authorities are contacting Holiday Inn Airport workers and other primary close contacts, who are being told to immediately isolate, get tested and remain isolated for 14 days.
About 80 staff members have so far been stood down or are in isolation, Ms Neville said.
A number of public exposure sites have also been identified, including Marciano's Cakes in Maidstone, Dan Murphy's in Sunshine and Off Ya Tree Watergardens in Taylors Lakes.
Anyone who visited the locations at the times listed on the are being urged to get tested and isolate immediately for the full 14 days.
In response to the new infection, Ms Neville said the government were continuing to make changes to strengthen the hotel quarantine program, including forcing staff to undergo COVID-19 testing on their days off from Monday.
"Our key aim here is to not just have a robust hotel quarantine program, but a robust outbreak management team and contact-tracing system," she said.
The new case comes as thousands of tennis fans are expected to swarm Melbourne Park for the opening day of the Australian Open on Monday.
Rafael Nadal of Spain is seen during a practice session at Melbourne Park Source: AAP
On Wednesday, a 26-year-old hotel quarantine worker at the Grand Hyatt hotel, one of three facilities used to quarantine Australian Open players, officials, and staff, tested positive to the virus.
No new cases have been detected among the man's close contacts since he tested positive, despite genomic sequencing confirming he was infected with the .
The breach forced more than 500 tennis players and their entourage to isolate as casual contacts of the infected worker.
All eventually tested negative and were released.
