Test results confirm Victoria's latest COVID-19 case caught the virus in hotel quarantine in South Australia.
The Victorian health department says it has received genomic sequencing test results which support their hypothesis that the case acquired the virus in hotel quarantine.
The Wollert man tested positive on Tuesday after returning from India via the Maldives and Singapore in April, and underwent two weeks of hotel quarantine at the Playford Hotel in Adelaide.
But he was staying in a hotel room next to another person who tested positive to the virus, and it appears both have the same strain.
Meanwhile, health authorities are racing to track down hundreds of fans who went to last Friday's AFL match on the same train as the man.
There are fears crowds of people may have been exposed to the virus on the Craigieburn line train while travelling to or from the Geelong-Richmond match at the MCG.
Victoria's Health Minister Martin Foley said a large number of people may have been exposed on the train or at the station.
"It's in the many hundreds, particularly the later train back, because it was after the AFL game," he told the media on Wednesday.
The AFL has sent text messages alerting all of the 54,857 people who attended.
The Craigieburn to Southern Cross service between 5.28pm and 6.07pm on Friday has been listed as a tier two exposure site, along with the Flinders St to Craigieburn service between 10.20pm and 11.05pm.
Craigieburn and Southern Cross stations last Friday night have also been listed as tier three exposure sites.
Authorities are working with metro trains to contact passengers, and have urged anyone who was on the train to isolate and get tested.
Messages have also been sent to almost 400,000 people who live near the exposure sites.
Also on Wednesday, Mr Foley warned people will soon face tough penalties if they don't use QR check in codes at venues, after some patrons at a new exposure site failed to use the system.
The Wollert case dined out at the CBD restaurant Curry Vault on Friday, but many people who were there at the same time failed to use the QR system.
Authorities are chasing down patrons and staff at the restaurant by working through records of takeaway orders and credit card transactions.
But so far the test results are promising.
Of the 28 people who were at the Curry Vault restaurant, 16 have so far returned negative tests.
Opposition frontbencher David Davis said the government was partly responsible for the QR code lapse, with its Service Victoria system to only become mandatory at the end of May.
"That stands in stark contrast to NSW and many of the other states," the Liberal MP told reporters.
Another 11 of the 17 people who came into contact with the infected man at the Pact Altona North warehouse have tested negative.
And five of the eight people at the Indiagate Epping exposure site have tested negative, while nine of the 28 contacts from Epping Woolworths have returned negative tests.
All three of the man's household contacts have tested negative.
People who travelled on Jetstar flight JQ771 from Adelaide to Melbourne on May 4 are also being urged to get tested.
More than 21,000 tests have been conducted in the past 24 hours.
Victoria has gone 75 days without a locally acquired case.
Australian Associated Press