The state recorded seven local COVID-19 cases on Thursday, including one case where the source of transmission is unknown - a testing site traffic controller.

All other cases have been linked to Victoria's current outbreaks and were in isolation for their entire infectious period.

It takes the number of cases linked to the state's outbreak of the highly infectious Delta variant to 204.

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More than 42,000 test results were received in the past 24 hours, while about 19,000 vaccine doses were administered at state-run sites during the same period.

It comes as authorities continue to investigate the source of the traffic controller's infection and isolate his close contacts.

Premier Daniel Andrews says authorities still don't know the source of the case, but genomic testing results are expected later on Thursday.

"That won't necessarily give us 100 per cent certainty, but it'll give us a really good steer," he told reporters.

The man, who worked at the Moonee Valley Racecourse site, tested positive on Wednesday, two days after developing symptoms.

The testing site was immediately closed and dozens of staff who worked the same shifts as the man were sent home to isolate as a precaution.

The drive-through testing centre, now listed as a tier-three exposure site over two days, will reopen on Thursday following a deep clean.

Meanwhile, proposals to host massive crowds at the AFL grand final and Melbourne Cup have been floated despite the current ban on large event gatherings.

Former Collingwood president Eddie McGuire has revealed a plan, purportedly driven by Bruce Keebaugh from The Big Group and Dr Ian Naughton from Respond Global, to get up to 100,000 people to the MCG for the AFL decider in September.

It would involve erecting a "ring of steel" around Melbourne's sports precinct and setting up 200 sites to carry out rapid antigen testing for all fans and officials.

VRC chief executive Steve Rosich also wrote an email to members this week outlining a plan to allow 60,000 spectators to attend the Melbourne Cup in early November.

Mr Andrews said all events would be assessed on a case-by-case basis.

"I can't tell you how many people will be at the grand final, but I'm determined to have people at the grand final and as many as we can safely get in," he said.

"The same for the racing carnival, the same for Harry Potter, the same for Moulin Rouge."

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