Border officials are investigating two other arrivals linked to the Australian Open who may have travelled to the country unvaccinated, as world number one Novak Djokovic fights to stay in the country.
Djokovic's visa was cancelled by the government on Thursday after he fell foul of entry requirements surrounding his COVID-19 vaccination status.
Now Home Affairs Minister Karen Andrews said other tournament attendees are being investigated for similar circumstances.
"If Australia Border Force becomes aware there is an issue, they will continue to investigate and make sure that Australia's entry requirements are maintained," she told the Seven Network on Friday.
"(ABF) will continue the investigations and once it is finalised, I'm sure that I will be briefed."
Ms Andrews said Djokovic, who is being held in detention pending his threatened deportation, had failed to provide the right information to enter Australia.
"It is required of anyone who is entering the country. If that information cannot be provided, then entry requirements to Australia have not been met," she said.
"One of those requirements is that you have to have proof that you are vaccinated against COVID."
The nine-time Australian Open champion, who arrived in Melbourne close to midnight on Wednesday, was formally denied entry about nine hours later and is being held in an inner north Melbourne hotel while he mounts a legal challenge against the deportation order.
His case began on Thursday in the Federal Court and will return on Monday for a final hearing.
The Serbian superstar has argued he had a vaccination exemption allowing him to travel to Australia.
Supporters of Novak Djokovic protest and sing with candles in the Melbourne suburb of Carlton on 6 January. Source: AAP
But it appears he only had an exemption provided by Tennis Australia and the Victorian government to participate in the competition.
Djokovic has not publicly revealed his vaccination status but it's believed he is unvaccinated and was relying on his previous infection with COVID-19 to gain entry to Australia.
Djokovic could be called to give evidence virtually in court on Monday.
Former Immigration Department deputy secretary Abul Rizvi told ABC radio the ABF and government response to Djokovic's visa issue was poorly handled.
"To wait until he arrived at the border and then cancel the visa is extraordinarily poor practice," he said.
"The process used for Novak Djokovic is simply unworkable at any scale."
But Finance Minister Simon Birmingham said the government had always been clear about the rules for people entering the country since the borders reopened in December.
"We made that clear to Tennis Australia - it's been publicly clear for a long time. You have got to be double vaccinated if you are not an Australian citizen to enter Australia," he told the Nine Network.
Meanwhile, Djokovic's family in Serbia has rallied around the champion, accusing the federal government of keeping him in captivity and comparing him to Jesus.
Serbian tennis player Novak Djokovic's father Srdjan (centre right) and mother Diana (left) arrive for a protest of support for their son in Belgrade, Serbia. Source: AAP
"They're keeping him in captivity. They are trampling on Novak and thus they are trampling on Serbia and the Serbian people," Djokovic's father Srdjan said at a news conference in Belgrade on Thursday.
"(Australian Prime Minister, Scott) Morrison and his like have dared attack Novak to bring Serbia to its knees.
"They crucified Jesus and now they are trying to crucify Novak the same way and force him on his knees."
Despite the situation, Ms Andrews said the tennis star would not be receiving any special treatment.
"We have always been clear that Mr Djokovic will be treated the same as everyone else in similar circumstances here in Australia," she said.
A rally in support of Djokovic will be held outside The Park Hotel in Carlton, where he is being held alongside about 30 asylum seekers, on Friday.
The Australian Open begins on January 17.
