The woman tested positive on Sunday after she completed a shift as an authorised officer at the hotel.
She had previously tested negative after a shift on Thursday. She did not work on Friday or Saturday.
Emergency Services Minister Lisa Neville, who is responsible for the quarantine program, said the woman's role consisted of issuing detention notices to international arrivals as they enter the hotel or are moved to another facility.
She did not work on the floor of the hotel.
"At this stage, when we had a look through just this person's engagement with people as they enter the hotel, as they exit the hotel, as they get moved to health hotels, it appears that there's no breach," Mr Neville said.
She said authorities are awaiting the results of genomic testing to see how the woman contracted the virus.
"We are also checking rosters and checking her movement through the hotel, whether there was any engagement with anyone who was positive," Ms Neville said.
The woman has been 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.
So far, 80 hotel quarantine staff, nine police officers and 12 Australian Defence Force members have been stood down.
Fifteen close contacts of the woman have also been identified and are isolating.
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.
More than 1200 of the 26-year-old's close and secondary contacts are self-isolating, with 80 per cent returning a negative test result.
Health Minister Martin Foley 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, with the tournament beginning at Melbourne Park on Monday.
Health Alert for low-level nsw case
A health alert has been issued for a Sydney cafe and venues in the Illawarra after a returned traveller tested positive for COVID-19 after completing their 14-day quarantine period.
NSW recorded no new locally acquired cases of COVID-19 in the 24 hours to 8pm on Sunday after issuing the alert on Sunday night.
NSW Health said the state had gone 22 consecutive days without a locally acquired case as the source of the latest infection was still under investigation.
"Investigations ... suggest the infection was likely acquired overseas and there is no indication at this stage that there was transmission in the hotel quarantine setting," a statement said.
Close contacts of the case who are not associated with the venues have been identified and are in self-isolation.
The latest alert applies to a cafe at Brighton Le Sands in Sydney's south as well as shops, a hotel and a beach in Wollongong and the Illawarra after the returned traveller visited them last week.
NSW Health says anyone who visited the venues around the same time should get tested immediately and self-isolate.
The person tested positive on the 16th day after arriving home, having returned two negative tests during their 14-day quarantine period, the department said on Sunday night.
"Test results indicate that the person has a low level of infection and their household contacts have returned negative results to date."
NSW has introduced non-compulsory "day 16" testing for overseas travellers in a bid to pick up cases that might develop at the tail end of the 14-day incubation period.