This winter’s Nordic World Ski Championships in Seefeld, Austria, terminated this season with a big doping scandal.

According to the report by the German News Channel ARD, 21 athletes from eight countries are suspected of blood doping. Several German athletes, whose names have not been revealed for the moment, are concerned.

The scandal broke out after a video leaked showing Austria’s cross-country skier, Max Hauke, allegedly in the middle of a doping process.

Doping refers to blood transfusion when the athlete’s blood is taken out and re-injected before the competition. This results in a boost of red blood cells that brings more oxygen to the muscles. Consequently, an increase in stamina is triggered, which potentially improves performance while practicing physical exertion.