The World Anti-Doping Agency (WADA) has said it would launch an independent review of a case related to 23 Chinese swimmers after international backlash.
The investigation, to be led by Swiss prosecutor Eric Cottier, will look into how the swimmers avoided punishment despite testing positive for a banned substance.
WADA said Cottier would have access to all files related to the case and be free to consult independent experts and is expected to deliver his findings within two months.
The agency's move follows a backlash from athletes and national anti-doping authorities who have questioned its processes and complained about a lack of transparency in the case.
"WADA’s integrity and reputation is under attack," WADA President Witold Banka said in a statement.
"WADA has been unfairly accused of bias in favor of China by not appealing the CHINADA case to the Court of Arbitration for Sport," he added, referring to China's anti-doping agency and sport's highest court respectively.
"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."
WADA said it would also send a compliance audit team to China to assess the nation's anti-doping programme and invite independent anti-doping auditors to join the mission.
Calls for an independent investigation have grown since the New York Times reported 23 Chinese swimmers tested positive for trimetazidine (TMZ) months before the COVID-delayed Tokyo Olympics in 2021.
The swimmers were cleared by a Chinese investigation which said they were inadvertently exposed to the drug through contamination. The report determined the swimmers were staying at a hotel where traces of TMZ were discovered in the kitchen.
TMZ is a medication that increases blood flow to the heart and is used to treat angina. It has been banned by WADA since 2014. Russian skater Kamila Valieva tested positive for the drug before the 2022 Beijing Winter Olympics.
WADA accepted China's findings and the case was not made public.
Following the NYT report, WADA defended its handling of the case, saying it had no evidence to challenge China's findings and that external counsel had advised against appealing them.
United States Anti-Doping Agency (USADA) Chief Travis Tygart, who accused WADA of being involved in a "potential cover-up" last week, dismissed the new investigation and CHINADA audit as toothless.
"By calling this an 'independent' investigation, WADA leadership is trying to pull the wool over our eyes," Tygart said in a statement.
"The world’s athletes deserve a truly independent review commission with a wide scope of review that is constituted with an independent athlete representative.
"A truly independent investigation also requires investigation of facts on the ground in China related to this case to include interviews of hotel staff, athletes, coaches."
Australia's anti-doping agency, which had also called for a review into the Chinese case, welcomed WADA's move.
Sport Integrity Australia boss David Sharpe said he hoped the review would provide clarity and "ensure faith is maintained in the global anti-doping system" in the lead-up to the Paris Olympics and Paralympics.