A hotel quarantine worker at the Holiday Inn at Melbourne Airport has tested positive to coronavirus.
The woman tested positive on Sunday after she completed a shift as an authorised officer at the hotel, the Department of Health confirmed in an alert just before midnight.
She had previously tested negative after a shift on February 4.
The woman is working with contact tracers who have already identified a number of potential exposure sites in Melbourne's west.
Authorities are also contacting Holiday Inn Airport workers and other primary close contacts, who are being told to immediately get tested and then isolate for 14 days.
Testing capacity at nearby exposure sites will be scaled up, with increased opening hours, additional staff and new pop-up sites to be confirmed.
It comes after a hotel quarantine worker at Melbourne's Grand Hyatt tested positive for the infectious UK strain of the virus last week.
About 1100 of the 26-year-old's close and secondary contacts are self-isolating, with 70 per cent returning a negative test result.
"They are the real heroes of this response over the past few days - stepping up, doing the right thing," Health Minister Martin Foley told reporters on Sunday.
He said it could be at least a week before authorities are confident they have contained that outbreak.
The Grand Hyatt was one of three hotels used as part of the Australian Open's quarantine program, and 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.
The tournament begins at Melbourne Park on Monday.
Meanwhile, a potential case of guest-to-guest transmission at the Park Royal hotel was also identified last week.
Emergency Services Minister Lisa Neville, who is responsible for the quarantine program, has confirmed a ventilation review of all hotels has been initiated and face shields made mandatory among workers.
NEW COVID-19 CASE EXPOSURE SITES
Visitors to the following venues at the specified times must immediately get tested and isolate for 14 days:
Friday, February 5
* Marciano's Cakes, Maidstone, 9.45am - 10.25am
* Dan Murphy's, Sunshine, 5.50pm - 6.30pm
Saturday, February 6
* Off Ya Tree Watergardens, Taylors Lakes, 1.17pm - 1.52pm
* Dan Murphy's, Sunshine, 6.50pm - 7.30pm
© AAP 2021
Photo: Victorian Health Minister Martin Foley (AAP Image/Erik Anderson)