Japan's legendary grand champion Kitanoumi was expected to resign as the head of the country's ruling sumo association Monday amid a widening scandal over marijuana use by wrestlers, reports said.

Kitanoumi, one of the modern era's greatest sumo champions, decided to quit as head of the Japan Sumo Associatwion after a Russian wrestler at his stable tested positive for marijuana, public broadcaster NHK and other media said.

Sumo officials could not immediately confirm the reports, which quoted unidentified sources.

The association carried out surprise urine tests involving 69 wrestlers, with Russian brothers Roho and Hakurozan testing positive for marijuana.

Roho, 28, whose real name is Soslan Boradzov, and Hakurozan, 26, whose name is Batraz Boradzov, both flatly denied smoking marijuana. Hakurozan trains at Kitanoumi's stable.

The test came just weeks after another Russian wrestler was arrested for marijuana possession, leading the sumo association to take the unprecedented step of expelling him.

Marijuana is strictly forbidden in Japan, and the case of the Russians has become a furore in Japan, where fans expect wrestlers to be role models and to lead nearly ascetic lives focused on early-morning training and participation in ritual ceremonies.

Kitanoumi, 55, whose real name is Toshimitsu Obata, has been the chief of the 2,000-year-old sport since 2002.

He was monstrously strong in his peak days in the ring in the 1970s, and retains the record as the youngest wrestler to reach the top rank of "yokozuna" grand champion at the age of 21 years and two months.

But the sport's image has been seriously tainted in recent years due in part to the bad-boy antics of sitting Mongolian grand champion Asashoryu.

Its prestige fell further last year when a teenaged apprentice died after undergoing violent training by his stable.

Kitanoumi came under fire for defending sumo oficials and not increasing the transparency of the sport, which is often seen as consisting as much of sacred rituals as athletic competitions.