- Swimmers were cleared of doping after positive tests
- Wada has received criticism for handling of case
Travis Tygart, the head of the United States Anti-Doping Agency (Usada), said on Monday he has doubts about the effectiveness of an investigation into positive drug tests by 23 Chinese swimmers.
The World Anti-Doping Agency (Wada) has faced mounting pressure to explain how Chinese swimmers tested positive for a banned substance weeks before the Tokyo Olympics but escaped punishment, with some going on to win gold medals.
