Victoria has recorded no new local COVID-19 cases for the second day after a Melbourne man tested positive.
His positive test on Tuesday sparked a contact tracing blitz, with hundreds of train passengers on two metropolitan services last Friday night alerted.
Victoria had one new overseas case on Thursday morning, with 21,984 test results.
The man's infection has prompted returned travellers on a South Australian hotel quarantine floor being ordered into another two weeks of isolation.
Genomic sequencing testing has confirmed the man became infected while staying at Adelaide's Playford Hotel.
He tested positive on Tuesday after returning from India via the Maldives and Singapore on April 19 and completing 14 days of hotel quarantine.
The man, from Wollert in Melbourne's outer north, was staying in a room next to another person who tested positive before being moved to a medi-hotel.
In a statement late on Wednesday, SA Chief Health Officer Nicola Spurrier confirmed the two cases had been genomically linked.
"Investigations into the precise cause of transmission are ongoing," she said.
Professor Spurrier said discharged returned travellers on level three of the Playford Hotel during the "period of concern" must now isolate for a further two weeks.
The group includes 10 South Australians who will be given the option to quarantine at home if deemed suitable.
Prof Spurrier stressed most medi-hotel staff working at the time of the suspected leak had undergone daily testing, although five still need to be followed up.
SA authorities earlier barred travellers from entering the state if they had visited any of Victoria's high-risk exposure sites, with few exceptions.
It came as Victorian health colleagues scrambled to track down hundreds of fans who went to last Friday's AFL match on the same train as the infected Wollert man.
There are fears hordes may have been exposed to the virus on the Craigieburn line train while travelling to or from the Geelong-Richmond match at the MCG.
The AFL sent text message alerts to all 54,857 spectators.
Victoria's Health Minister Martin Foley warned people will soon face tough penalties if they fail to check in with QR codes at venues, after some patrons at a new exposure site failed to use the system.
The Wollert man dined at the CBD restaurant Curry Vault on Friday but others failed to use the QR system, which is to become mandatory for venues later this month.
Victoria has gone 76 days without a new local infection.
