Health authorities are racing to track down hundreds of fans who went to last Friday’s AFL match on the same train as a man with COVID-19.

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 also working with metro trains to contact passengers, and have urged anyone who was on the train to isolate and get tested.

The state has not recorded any further positive results after the Wollert man tested positive on Tuesday, with more than 21,000 tests conducted in the past 24 hours.

It means Victoria has gone 75 days without a local case.

The man, in his 30s, flew into Adelaide from India via the Maldives and Singapore on April 19 before Australia’s flight ban on returnees from India began.

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.

Of the 18 patrons that have been tested, three have so far tested negative, and another 14 patrons have since been contacted.

Mr Foley described the incident as a “wake-up call”.

Victorians could return to tighter restrictions if evidence emerges the man infected others in the community.

Authorities are chasing down patrons and staff at the restaurant by working through records of takeaway orders and credit card transactions.

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.

There are a further 17 primary close contacts of the positive case, linked to shops in Altona North.

The department is awaiting the results of genomic testing to confirm how the latest case was infected.

After completing quarantine in South Australia at the Playford Hotel, the man returned to his home in Melbourne’s Wollert early last week and developed symptoms on Saturday, before testing positive on Tuesday.

SA authorities are examining whether the man contracted the virus before his arrival and had an unusually long incubation period, or caught it from a person in a neighbouring hotel room.

Victoria’s Chief Health Officer Brett Sutton suspects the man picked it up in the hotel, and not in India or during his international flights.

But people who travelled on Jetstar flight JQ771 from Adelaide to Melbourne on May 4 are also being urged to get tested.

All three of the man’s household contacts have tested negative.