WADA released a statement saying, "The World Anti-Doping Agency (WADA) is astonished by the outrageous, completely false and defamatory statements made by the CEO of the United States Anti-Doping Agency (USADA), Travis Tygart, who has made very serious accusations against WADA in connection with the case of 23 swimmers from China reported in the media earlier today.

"Mr Tygart's allegations are politically motivated and designed to undermine WADA's work to protect clean sport around the world. WADA notes that the damaging comments have been made without any supporting evidence.

"The truth is that, according to all the available scientific evidence and information that has been collected, evaluated and tested by leading anti-doping experts, WADA had no basis to question the environmental contamination explanation. At all times, WADA acted in good faith, in accordance with due process, and following advice of external counsel when it decided not to appeal this case." 

It continued, "In the absence of any other evidence, WADA continues to stand by the results of its rigorous scientific investigation and the actions of its Intelligence and Investigations Department. WADA's statement of 20 April outlines in more detail the Agency's position on this matter.

"It is implicit in his statement that Tygart does not accept the finding of environmental contamination in this case, although he cannot say why. However, it is true that in the United States, WADA has also accepted USADA's similar conclusions of contamination involving a number of US athletes. Tygart should be aware that it is not only American athletes who can be victims of contamination through no fault of their own.

"USADA contacted WADA in early 2023 based on a tip it had received about an alleged cover-up involving these cases but unfortunately was unable to provide any evidence whatsoever. It should be noted that following Mr. Tygart's false allegations, WADA has no choice but to refer this matter to its legal counsel for further action," the WADA statement concluded.

The war of words escalated on Saturday with Tygart making a statement of his own. He expressed his disappointment at WADA's "threats and scare tactics when confronted with a blatant violation of the rules governing anti-doping".

He added, "When you blow away their rhetoric, the facts remain as have been reported: WADA failed to provisionally suspend the athletes, disqualify results, and publicly disclose the positives. These are egregious failures, even if you buy their story that this was contamination and a potent drug ‘magically appeared’ in a kitchen and led to 23 positive tests of elite Chinese swimmers."

"Yes, there are contamination cases, and we’ve been advocating for years to change the WADA rules for those substances that can potentially cause contamination," Tygart continued. "TMZ is not in that category. And, most importantly, in all contamination cases that we have proven, we provisionally suspended the athlete, disqualified the results, found a violation, and issued an announcement as required by the rules. Transparency is the key to shining the light in the darkness, and here, by not following the rules, WADA and CHINADA have left clean athletes in the dark."

Russian figure skater Kamila Valieva tested positive for TMZ at the Beijing 2022 Winter Olympics. She was initially cleared by the Russian Anti-Doping Agency (RUSADA) after food contamination was blamed, but WADA appealed with the teenager handed a four-year ban.

This is far from the first time USADA and WADA have clashed. In September 2018, Tygart called WADA's decision to reinstate RUSADA after a three-year ban following allegations of state-sponsored doping "a devastating blow to the world’s clean athletes" and urged that WADA be reformed.