Sport authorities of China have warned their athletes and coaches to stay away from any kind or efforts of doping in their preparation for the London Olympic Games.

Heads of associations of Olympic sports, training bases, and provincial sport bureaus were summoned by China’s General Administration of Sport for signing a “responsibility agreement” and committing to the anti-doping drive, sportsmanship, and good discipline at the London Games.

China has been a “vigorous fighter” against doping but the challenge should not be underestimated, China’s General Administration of Sport head Liu Peng said.

China Anti-Doping Agency (CHINADA) recently announced four positive cases, including that of swimming world champion Li Zhesi who was found positive for performance-enhancing drug erythropoietin (EPO) in an out-of-competition test in March.

The other three positive cases were from athletes belonging to rowing, athletics, and tug of war and not London-bound.