Genomic sequencing testing has confirmed a Melbourne man became infected while staying at the Playford medi-hotel on North Terrace.

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 for the virus before being moved to Tom’s Court – Adelaide’s dedicated medi-hotel for COVID-positive travellers.

In a statement late on Wednesday, Chief Public Health Officer Nicola Spurrier confirmed the two cases were genomically linked.

“Investigations into the precise cause of transmission are ongoing,” she said.

Prof 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.

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.

Earlier in the day, Police Commissioner Grant Stevens barred travellers from entering the state if they had visited any of Victoria’s high-risk exposure sites, with few exceptions.

The sites are listed on the Victorian Department of Health website and include businesses in the suburbs of Altona North, Craigieburn, Docklands, Epping and Melbourne.

Stevens also announced on Wednesday that plainclothes police officers will now be monitoring whether individuals and businesses are properly using the QR code check in system.

It comes as Victorian health colleagues scramble 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 on Friday night.

The AFL has 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.

No other new cases were recorded in Victoria on Wednesday from more than 21,000 tests, while SA recorded one new case from a returned traveller in hotel quarantine.