China discloses Sun Yang's earlier doping ban

Chinese Olympic and world champion swimmer Sun Yang was banned for three months in May after failing a doping test. China's anti-doping agency disclosed the incident four months later, raising questions over why the positive test was kept quiet for so long. 

Sun tested positive for the banned stimulant trimetazidine on May 17 during China's national swimming championships in Hangzhou.

The suspension began immediately and ended on August 17, prior to Sun's appearance in September at the Asian Games at Incheon, South Korea, where he won three gold medals.

The World Anti-Doping Agency reviewed the full case file and decided not to appeal against the decision by the Chinese Swimming Federation to impose a three month sanction.