A leaked email from Tennis Australia to Australian Open players says two people aboard their flight to Melbourne have tested positive for Covid-19.
The email declares they will be sent into hard lockdown and unable to leave their rooms for 14 days, after catching flight QR7493 from Los Angeles to Melbourne and being exposed to the virus.
"Unfortunately we have been informed by the health authorities that two people on your flight from LAX that arrived at 5:15am on Friday 15 January have returned positive COVID-19 PCR tests on arrival to Melbourne," the Tennis Australia email read.
"We know this is not how you imagined your preparations for the AO would start but our entire team is here to support and do everything we can to get your through this.
"You will soon be contacted by our medical experts Aspen Medcal if you haven't been already. They are available 24/7 to support you with all your medical, mental health or wellbeing concerns.
"The most important thing you need to know right now is you are not alone in this and we are here to provide you any extra support you need."
Players on the flight reportedly include female stars Victoria Azarenka and Sloane Stephens and men's star Kei Nishikori.
The news, which broke on Saturday morning local time, has made headlines around the world.
New York Times sports journalist Karen Crouse wrote that she feels "terrible" for the players aboard who now won't be allowed to practice for the next two weeks except on the exercise bikes the Australian Open delivered to their rooms".
She tweeted: "In the name of full transparency, I hope the Australian Open will divulge the names of the passengers on the LAX charter flight who tested positive in their day-of-arrival Covid test."
It follows news that former world number 1 Andy Murray had tested positive for COVID-19.
Health chiefs vowed Friday there will be no preferential treatment for the five-time finalist, saying he must return a negative Covid-19 test if he wants to play the Australian Open.
The former world number one was due to travel to Melbourne on one of a series of charter flights laid on by tournament organisers, but revealed on Thursday he had tested positive for the virus.
He is isolating at home in London, casting major doubt over whether he will be able to play the opening Grand Slam of the year.
Britain's Press Association news agency said the three-time major winner, apparently in good health, was hoping to arrive in Australia at a later date.
But Victorian state health minister Martin Foley said the Scotsman won't be getting any special favours.
"In regards to Mr. Murray, we've been clear from the start that anyone who tests positive is not able to be part of the programme coming into Melbourne and Australia," he told reporters.
"Mr. Murray, and the other 1,240 people as part of the program, need to demonstrate that if they're coming to Melbourne they have returned a negative test.
"So should Mr. Murray arrive, and I have no indication that he will, he will be subject to those same rigorous arrangements as everyone else. Should he test positive prior to his attempts to come to Australia, he will be refused." Murray was handed a wildcard to the Open, hoping to make his first appearance in Melbourne since 2019, when he revealed the extent of a right hip problem and raised the possibility of imminent retirement.
More than 1200 players and support staff have begun arriving for 14 days' quarantine ahead of the delayed tournament, which is due to start on February 8.
They are being greeted by biosecurity officials wearing personal protective equipment, before being whisked away to hotel quarantine.
Players are only allowed into the country with proof of a negative test prior to departure, or with approval as a recovered case at the Australian government's discretion.
That rule applied to American world number 50 Tennys Sandgren, who was permitted onto a flight from Los Angeles Thursday despite tweeting that he tested positive this week.
It was his second positive result, having been diagnosed with Covid-19 in November.