According to his manager, Peet van Zyl, the 28-year-old was set to return to action for the first time since February when the South African athletics season was cut short due to the COVID-19 pandemic.

Rio 2016 Olympic champion Van Niekerk has been absent since 2017 due to suffering an anterior cruciate ligament tear in a touch rugby celebrity match.

He became the world record holder in the 400m final at Rio 2016, running a time of 43.03sec to break Michael Johnson's previous record of 43.18 from the 1999 World Championships in Seville in Spain.

At the Trieste event, the South African, who is regarded as one of the best sprinters of all time, was expected to run the 100m and 400m.

He became the first sprinter to run under 10 seconds for 100m, 20 seconds for 200m and 44 seconds for 400m in history.

Recently, the sprinter made it to his European home of Genoma in Italy to train and compete over the next three months.

But Van Zyl said that his athlete's test seemed to be a "false positive" when speaking to Italian publication Independent Media.

He stated that a blood test showed Van Niekerk's results may have been negative.

His first three tests were negative before a fourth turned positive and a fifth showed up negative, but he was forced to follow protocol.

"We are all in isolation, not mixing with other people and staying on a separate floor," said Van Zyl. 

"We even have our meals alone.

"We will follow the protocol here, and then decide when Wayde will next race."

Long jumper and training partner Ruswahl Samaai decided to withdraw from the competition after stating he did not feel comfortable competing.

The two are joined by sprint hurdler Antonio Alkana as well as coaches Ans Botha and Jenny Kingwill.

All five had three negative tests each after their arrival in Italy.