Tennys Sandgren was cleared to board a flight from the United States bound for Melbourne ahead of the Australian Open despite revealing he returned a new positive coronavirus test this week. 

The American, twice a quarter-finalist at Melbourne Park, initially posted to social media on Wednesday that he had tested positive for the virus for a second time. 

Although his first instance of having the illness was recorded in November, the 29-year-old's participation in the tournament appeared to be in doubt. 

But, as he continued to update followers through the day, it emerged he had been allowed to board his flight. 

Writing on Twitter, he said: "Wait hold on I think they are trying to get me on 15 min [sic] after the plane was supposed to depart.. my bags still aren't checked lol." 

A follow-up read: "Wow I'm on the plane. Maybe I just held my breath too long. Craig Tiley [Tennis Australia] is a wizard." 

Some expressed concerns about the possibility of Sandgren potentially spreading the virus to fellow passengers and then locals once he arrives in Australia. 

But a statement from the Australian Open has looked to reassure people that players' infectiousness is checked prior to boarding flights. 

It read: "In the case of Tennys Sandgren, who has self-disclosed that he previously tested positive in late November, his medical file had to be reviewed by Victorian health authorities. Upon completion of that review he was cleared to fly.

"Any recovered case must go through this process in order to have an opportunity to travel here for the Australian Open. No one can travel without either proof of a negative test or this special clearance from authorities confirming they are not infectious. 

"Upon arrival all players are immediately placed in a secure quarantine environment for 14 days under the authority of COVID Quarantine Victoria, and will undergo a more rigorous testing schedule than most returning travellers." 

An earlier statement issued by the tournament organisers in reply to Sandgren's tweets said: "Some people who have recovered from COVID-19 and who are non-infectious can continue to shed the virus for several months. 

"Victorian Government public health experts assess each case based on additional detailed medical records to ensure they are not infectious before checking in to the charter flights. 

"Players and their teams are tested every day from their arrival in Australia, a much stricter process than for anyone else in hotel quarantine." 

The first grand slam of the year is due to begin on February 8 after being delayed due to the pandemic. 

Initially it was to run from January 18-31 but was pushed back to help give qualifiers time to travel and complete a two-week quarantine in Australia prior to warm-up events getting under way at the end of the month. 

Players at Melbourne Park will have to follow strict guidelines and protocols, including a five-hour limit on training with a maximum of one team member. 

The teams must stay in their hotel for the other 19 hours of every day, and players have to return six negative COVID-19 tests before being allowed to play.