The head of Japan’s sumo association has resigned in the wake of a string of scandals to hit the ancient sport, including suspicions that wrestlers had smoked marijuana.

Two Russian wrestlers tested positive for marijuana last week, setting off a media frenzy about the sport, which historians say dates back 2000 years.

Roho and Hakurozan, who are brothers, denied smoking the drug, but the tests came shortly after another Russian wrestler was arrested and fired for suspected marijuana possession.