RIO DE JANEIRO - The Chinese Swimming Association will launch a thorough investigation into the positive doping result turned in by swimmer Chen Xinyi, who was expeled from the Rio Olympics on Thursday.

File photo of Chen Xinyi

The Court of Arbitration for Sport (CAS) disqualified the 18-year-old swimmer who had tested positive for the diuretic hydrochlorothiazide after her fourth-placed finish in the women's 100m butterfly on August 7.

"The Chinese Olympic delegation has demanded the Chinese swimming body to start a full investigation into the matter in order to clarify the facts and seek out the truth," said the delegation in a statement sent to Xinhua News Agency.

"The delegation will punish those responsible in accordance with the truth and law."

The statement reaffirmed China's zero tolerance policy against doping, saying the country conducts 15,000 doping tests annually and only 2 out of 1,000 have failed checks in recent years.

"Although we have been making progress in battling performance-enhancing drugs, this case once again serves as a warning that anti-doping campaign is a complicated and formidable task and needs longtime and consistent efforts," said the statement.

CAS said that it is up to the International Swimming Federation (FINA) to decide on the athlete' punishments following the Games.