Four more Australian Open participants, including one player, have been recorded with COVID-19 infections and more cases may come to light as testing continues, officials said on Monday.
Health authorities in Victoria state have now reported nine infections among passengers that arrived in Melbourne on charter flights for the February 8-21 Australian Open.
"All four are associated with the tennis, and they're all tucked away safely in hotel quarantine," Victoria state premier Daniel Andrews told reporters of the new cases.
Passengers on three Australian Open charter flights have now been sent into hard quarantine, including more than 70 players who are unable to train for 14 days ahead of the year's first Grand Slam.
"I think the people who tested positive thus far were probably exposed before they got on the flights," Victoria Chief Health Officer Brett Sutton said.
"But it will be the test results in coming days that will give us a picture of whether anyone's had infection transmitted to them on a flight.
"That's why the rules are extremely strict for these tennis players and their entourage, as much as for any other international arrival."
The growing infection count has sparked calls from pundits to cancel the Grand Slam.
"It’s time to be selfish, time for Victoria to put ourselves first," 3AW radio broadcaster Neil Mitchell said.
"Call off the Australian Open. It’s not worth the risk."
Tennis Australia boss Craig Tiley said on Sunday the tournament would start as scheduled but the governing body would look at altering the lead-up tournaments to help players unable to train due to quarantine.
Andrews said the government still supported holding the Grand Slam and backed health officials to deliver it safely.
"We think we've struck the appropriate balance," he said.
"If there was a sense from the public health team that that balance could not be struck, that it was too high a risk, well then we wouldn't have had the event."
Some players have complained about quarantine conditions and said they had not been advised that they would not be allowed to train if there were cases on their flights.
A Spanish tennis website reported that world number one Novak Djokovic had written to Tiley requesting that quarantine restrictions could be eased for players, including reducing the mandatory 14 days of isolation and having players moved to "private houses with tennis courts" so they could train.
The report drew a backlash from Australians on social media, with Djokovic and players told to check their "privilege".
Andrews said the biosecurity protocols would not be changed.
"It doesn't mean that everyone likes them, but that's not the world we're in," he said.
"This is a wildly infectious pandemic. There are rules that need to be followed."
Australia's biggest outbreak of COVID-19 started from returned travellers infecting staff at quarantine hotels in Melbourne, the state capital of Victoria, last year.
About 800 people died in the second wave of the outbreak and about five million people were plunged into a hard lockdown that lasted nearly four months.