The World Anti-Doping Agency (WADA) on Monday rejected accusations of a cover-up during their investigation into Chinese swimmers testing positive for a prescription heart drug and said they would take "whatever action necessary" in response to the allegations.

Reports at the weekend that 23 Chinese swimmers tested positive for trimetazidine (TMZ) -- which can enhance performance -- ahead of the Tokyo Olympics in 2021 led to a strong attack from the head of the United States Anti-Doping Agency (USADA), Travis Tygart.