The Chinese Swimming Association (CSA) confirmed that Chinese swimmer Chen Xinyi failed a doping test at the Rio Olympics.

Chen, 18, who finished fourth in the women's 100m butterfly final, tested positive for diuretic hydrochlorothiazide (HCTZ) on Sunday (Aug. 7), according to the South China Morning Post. HCTZ is a banned substance due to its ability to mask the use of other performance-enhancing drugs.

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The athlete has now appealed to the International Olympic Committee (IOC) to test her "B" sample and hold an evidentiary hearing over the matter.

"The CSA has taken this matter seriously and demanded full cooperation from Chen in the investigation," the CSA said.

"The CSA resolutely opposes use of banned substances. We will cooperate with the Court of Arbitration of Sport during its investigation and will respect the final ruling by the CAS."

The news comes hours before Chen was scheduled to participate in the 50m freestyle swimming competition on Friday morning  (local time). The positive drug results will further raise tensions surrounding doping at the Olympics.

China has been defending its athletes against doping accusations and recently asked Australian swimmer Mack Horton to apologize for calling Chinese swimmer Sun Yang a "drug cheat" following his loss to the Chinese superstar in the 400m men's freestyle final, according to CCTV News.

The failed drug test makes Chen the first Chinese athlete to test positive at the Olympic Games since 1992 in Barcelona. China's biggest doping scandal came to light in 1994 during the Asian Games in Hiroshima, where seven Chinese athletes failed their drug tests.

TagsRio Olympics, Rio, Olympics, china, Chen Xinyi, Doping, Drugs, Chen Xinyi drugs, Chen Xinyi doping, Sun Yang