MIAMI, United States (AFP) — The World Anti-Doping Agency (WADA) yesterday rejected accusations of a cover-up during its 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.

Tygart said that WADA and the Chinese anti-doping body had “secretly, until now, swept these positives under the carpet” and called the situation a “potential cover-up”.

The swimmers were allowed to compete after world governing bodies accepted China’s findings that they had ingested it unwittingly from food during a meet in late 2020 and early 2021.

Several went on to win medals, including gold, and many are in line to compete at the Paris Olympics this summer.

“What I can say right now is that at every stage, WADA followed the whole due process and diligently investigated every line of inquiry in this matter,” WADA president Witold Banka told an online news conference.

“If we had to do it over again now, we would do exactly the same thing.”

Banka said “no credible evidence of wrongdoing was provided by any source who came forward on this file, so the threshold for WADA intelligence and investigations to open an investigation was not met”.

He said the body had “no credible way to disprove the contamination theory that was accepted by CHINADA, a position that was also accepted by World Aquatics.

“In short, if we had taken such an appeal and challenged the contamination explanation, we would certainly have lost,” he said.

The WADA president said there was no question of his body being overly lenient on Chinese athletes.

“It is worth pointing out that at the same time as our experts were reviewing this case in 2021, we are also vigorously pursuing justice in the case of another swimmer from China, Sun Yang,” he said.

Three-time Olympic champion Sun is about to finish a second doping ban. His first, in 2014, was for taking TMZ.

Wenzel said WADA was going through comments made by USADA and others in media reports and a documentary by German broadcaster ARD with a “fine tooth-comb” and that the body would “take whatever action is necessary”.