Authorities are still waiting on test results from the contacts of Melbourne's most recent virus case and have found some patrons at a CBD Indian restaurant failed to use the QR code system, hampering contact tracing.

Of the infected man's 121 primary close contacts, 90 have returned negative tests so far.

The latest testing update comes as the state government announced businesses breaking check-in rules will face a $1652 on-the-spot fine, and further penalties of up to $9913 and prosecution for repeated breaches.

Checks last week showed more than a third of businesses are not complying with QR code rules.

It followed authorities dishing out 165 enforcement notices and 300 warnings as part of a three-week blitz of 4000 cafes, shops and restaurants in April.

The breaches included a lack of signage, failing to use QR codes, and not having a COVID-safe plan.

While most businesses are doing the right thing, Acting Police Minister Danny Pearson said others were "letting down" Victorians after the state fought to defeat its deadly second wave.

"As we've seen this week, it's essential every Victorian checks in when visiting a business, to help contact tracers quickly find those who could be at risk of coronavirus exposure," he said in a statement on Thursday.

The government's QR code system will only become mandatory for businesses from the end of May, with the opposition questioning why it didn't follow NSW's lead earlier.

"They've had months to get this right and they've failed to do so," shadow health minister Georgie Crozier told reporters.

An average of 28,000 check-ins are being registered on the system every day, with more than 91,000 businesses signing up.

Meanwhile, Victoria has recorded no new local COVID-19 cases on the second day after the Melbourne man's positive test sparked a contact tracing push.

The health department also updated testing figures of his primary close contacts, including the three people who share a house with the man.

They and another 87 of the 121 primary close contacts from four exposure sites - the Curry Vault restaurant, Pact Altona North, Indiagate Epping and Woolworths Epping - have tested negative.

Acting Premier James Merlino on Thursday morning said the rest of the results would come through within 36 hours, adding progress of the case was "pretty positive so far".

The man's infection has prompted returned travellers on a South Australian hotel quarantine floor to be ordered into another 14 days' isolation after it was confirmed he became infected while staying there.

"That's a good thing because we're not chasing unknown sources," Mr Merlino said.

The man, from Wollert in Melbourne's outer north, tested positive after returning from India via the Maldives and Singapore on April 19 and completing 14 days' hotel quarantine.

He was staying in a room at Adelaide's Playford Hotel next to another person who tested positive before being moved to a medi-hotel.

Victorian health officials are continuing to track down commuters 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, while Metro Trains has contacted registered Myki holders on the specific services.

Victoria has gone 76 days without a new local infection.

Australian Associated Press