COLORADO - The head of the United States Anti-Doping Agency (Usada) demanded on April 22 an investigation into the World Anti-Doping Agency's (Wada) handling of 23 positive tests by Chinese swimmers and welcomed the global body's threat of legal action.

During a nearly two hour Zoom call with the media Wada fired back at critics and provided detailed explanation of its decision not to pursue sanctions on the swimmers, who tested positive for trimetazidine (TMZ) months before the Covid-delayed Tokyo Olympics began in July 2021.