The World Anti-Doping Agency (Wada) and US Anti-Doping (Usada) are at loggerheads again after fresh reports that more Chinese athletes – one of whom is swimming at the Paris Olympics – have been cleared using a contaminated meat defence.

In a separate incident to the doping inquiry involving 23 Chinese swimmers that emerged in April, the New York Times reported that Tang Muhan and He Junyi both tested positive after eating french fries, Coca-Cola and hamburgers at a Beijing restaurant in October 2022.

However the Chinese Anti-Doping Agency (Chinada) subsequently ruled that the steroid came from contaminated meat from a burger and cleared both men. Tang is now expected to compete for China in the relay on Thursday.

Wada confirmed that the two swimmers had tested positive for “trace amounts” of metandienone in October 2022 – but said it was part of a wider number of positive tests in China involving meat contamination.

“The investigation by Chinada included the testing of hundreds of meat samples from various sources, with dozens revealing positive results for metandienone,” Wada said. “Chinada also analysed the athletes’ nutritional supplements and conducted hair tests, which were negative. Significantly, both the swimmers provided negative doping control samples in the days before and after the single trace positive.”

Usada reacted with anger at the statement and accused Wada of allowing China to “compete under a different set of rules tilting the field in their favour”.

Travis Tygart, the Usada chief executive, said: “A mountain of evidence shows that the system has failed, Wada has accepted China can play by its own set of rules, and the public is losing faith in the Olympic values.

“Not only will the upcoming swimming relay event be tarnished given that China swept this positive test for a hardcore steroid under the rug, but with it coming on the heels of Wada also allowing China to bury 23 positive tests of swimmers, clean athletes’ hopes and dreams have been stolen by these failures.”

Wada hit back accusing the US of trying to discredit it by implying wrongdoing. “The politicisation of Chinese swimming continues with this latest attempt by the media in the US to imply wrongdoing on the part of Wada and the broader anti-doping community,” it said in a statement.

“As we have seen over recent months, Wada has been unfairly caught in the middle of geopolitical tensions between superpowers but has no mandate to participate in that.”

Wada did acknowledge that it was worried about some athletes using contaminated meat as an excuse. “The matter raises again the wider issue of contamination, in particular, food contamination. Based on the number of cases, clearly there is an issue of contamination in several countries around the world.

“Apart from China, in particular, there have been several of these cases in the US in the past few months alone, where highly intricate contamination scenarios were accepted. The ongoing review of the World Anti-Doping Code and International Standards will provide an opportunity to consider possible solutions to this ongoing issue for clean sport.”