PYEONGCHANG • Japanese short-track speed skater Kei Saito vowed to clear his name yesterday after testing positive for a banned substance in the first doping case to hit the Pyeongchang Olympics.

The 21-year-old is the first Japanese to test positive at a Winter Games and he was immediately thrown out of the competition on Monday. The case will no doubt embarrass Japan, organisers of the Summer Games in 2020.

Saito returned positive tests for acetazolamide, an unauthorised diuretic which can be used to mask performance-enhancing drugs.

"I want to fight to prove my innocence because I don't remember (taking the drug) and it's incomprehensible," he said in a statement.

The Court of Arbitration for Sport (CAS), which handles doping cases during the Games, said he had left the athletes' Olympic Village voluntarily and would be provisionally suspended from all competition pending a full investigation.

Saito, a human biology student whose sister Hitomi is also competing in Pyeongchang, arrived at the Village on Feb 4. He was woken up at 2am the following morning by testers who took two samples.

"Both samples tested positive," said the head of the Japanese Olympic delegation Yasuo Saito, who is also the vice-president of the Japan Olympic Committee.

Saito, who was summoned before a CAS tribunal on Monday, insisted he was innocent of any wrongdoing He was tested before the Games on Jan 29 and found to be drug-free.

"As for the test results this time, the only possibility I can think of is that I accidentally and unconsciously put a banned substance in my mouth," he added.

"I've never used body-enhancing drugs so I don't think about hiding it. There's no merit or motive for me in using this medicine."

Meanwhile, several American cyber security firms said on Monday that they had uncovered a computer virus dubbed the "Olympic Destroyer".

It was likely used in an attack on last Friday's opening ceremony. Organisers confirmed the attack, saying it affected Internet and television services but did not compromise critical operations.

AGENCE FRANCE-PRESSE, REUTERS