The International Swimming Federation handed Junya Koga a provisional suspension, and he has been pulled from Japan's team for this year's Asian Games in Jakarta.

According to his agent, Koga's urine samples taken in a March 2 out-of-competition test contained a prohibited anabolic agent used to build muscle. The backup sample also tested positive.

After the Japan Swimming Federation announced Koga had failed the test, the 30-year-old backstroker said he has never intentionally taken a banned substance.

Koga says "my approach to doping has always been very strict, so I feel shameful and frustrated that a prohibited substance has come from my own body."