RIO DE JANEIRO, Aug. 12 -- Chinese swimmer Chen Xinyi has failed a doping test at the Rio Olympic Games, the Chinese Swimming Association (CSA) announced in its statement on Friday morning.

The 18-year-old Chen tested positive for hydrochlorothiazide, a diuretic, on Aug. 7 after she finished fourth in the 100m butterfly final in 56.72 seconds.

Chen has applied to the International Olympic Committee (IOC) for testing of sample B and a hearing to look into the matter, said the CSA.

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

"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."

Chen missed the podium in the 100m butterfly final on Sunday as she came fourth in 56.72 seconds, 0.09 behind bronze medalist Dana Vollmer of the United States. Sweden's Sarah Sjostrom won the event in a world record time of 55.48 with Canadian Penny

Oleksiak in second place in 56.46.

Chen was previously scheduled to take part in the women's 50m freestyle heats on late Friday morning.

In order to add accountability and transparency of the Rio Games, the IOC has adopted a new step in its doping control process.

After an adverse analytical finding appears, the IOC will first carry out the initial research to determine whether the athlete in question has any legitimate reason to take banned substance, according to an early statement from the Rio Olympics organizing committee.

Once the IOC decides there is a case to answer, the CAS will take over to determine whether an adverse finding translates into an anti-doping violation or not, said the statement.

The IOC then will mete out Games-related penalties like disqualification, added the statement.