The World Anti-Doping Agency demanded answers Friday after reports that Chinese swimming star Sun Yang was called up for national training for the Tokyo Olympics in an apparent breach of his doping ban.
The latest incident in the colourful career of the three-time Olympic champion comes two months after he was given an eight-year ban for refusing to provide a doping sample.
Unless he is successful with an appeal, the 28-year-old will not be eligible for the Tokyo Games in 2021 and his career is effectively over.
However, Chinese media said on Thursday that Sun had been included on a list of swimmers called up for national training between April 1 and June 30.
Media published a notice purporting to show Sun's name on the list for preparations for the Olympics, which have been moved to the summer of 2021 because of the coronavirus pandemic.
The Chinese Swimming Association (CSA) subsequently said that the 1500m freestyle world record-holder is "still serving (his) suspension.
"The previous notice is invalid," CSA said in a short statement.
But that may not satisfy WADA, who said in a short statement to AFP on Friday: "We are following up with the relevant authorities to establish the facts in this matter."