The under-fire World Anti-Doping Agency (WADA) has launched an independent review over its handling of a case that allowed 23 Chinese swimmers who tested positive for a banned substance to avoid punishment.

The investigation will be led by Swiss prosecutor Eric Cottier, who WADA said would have access to all files and documents related to the case and would be free to consult independent experts.

Cottier will begin his work in the coming days and is expected to deliver his findings within two months.

“WADA’s integrity and reputation is under attack,” WADA president Witold Banka said in a statement.

“In the past few days, WADA has been unfairly accused of bias in favour of China by not appealing the CHINADA case to the Court of Arbitration for Sport.

“We continue to reject the false accusations and we are pleased to be able to put these questions into the hands of an experienced, respected and independent prosecutor.”

Calls for an independent investigation have grown since a New York Times report on Saturday said 23 Chinese swimmers had tested positive for the banned drug trimetazidine (TMZ) months before the COVID-delayed Tokyo Olympics in July 2021.

The swimmers avoided sanctions after an investigation by Chinese authorities ruled the adverse analytical findings, or AAFs, were the result of being inadvertently exposed to the drug through contamination.

A report determined all the swimmers who tested positive were staying at the same hotel where traces of trimetazidine (TMZ), which is found in heart medication, were discovered in the kitchen.

WADA has defended its handling of the case, saying it had no evidence to challenge China’s findings and that external counsel had advised against appealing.

The United States Anti-Doping Agency (USADA) has led the call for an independent investigation, along with an overhaul of WADA to restore confidence in the global body ahead of the 2024 Paris Olympics.

USADA chief Travis Tygart has accused WADA of being involved in a “potential cover-up” and the global anti-doping body has responded by threatening legal action.

In addition to the independent prosecutor, WADA said it would send a compliance audit team to China to assess the state of its anti-doping program and will invite independent auditors from the broader anti-doping community to join the mission.

“While not one shred of evidence has been presented to support any of the allegations made against WADA, we wish to deal with the matter as quickly and as comprehensively as possible so that the matter is appropriately handled in advance of the upcoming Paris Olympic and Paralympic Games,” WADA director-general Olivier Niggli said.

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