TOKYO — A Japanese kayaker has been banned from competition for eight years for spiking the drink of a rival so that he would fail a doping test.

Yasuhiro Suzuki drugged his key rival at last year’s national championships in September. Suzuki spiked the drink of Seiji Komatsu with an anabolic steroid, causing him to fail a doping test, the Japan Anti-Doping Agency said Tuesday.

The Japan Canoe Federation began investigating after Komatsu tested positive but denied ever taking drugs.

After Komatsu tested positive, Suzuki admitted putting a muscle-building supplement containing the banned steroid methandienone in his drink.

The incident is Japan’s first case of an athlete failing a doping test due to deliberate contamination, according to the Japan Anti-Doping Agency, which handed down the eight-year ban.