Sports minister Ryu Shionoya has demanded that doping tests covering all active sumo wrestlers be conducted at an early date to root out marijuana use in the national sport.

Shionoya, minister of education, culture, sports, science and technology, met Monday with a group of advisers for the Japan Sumo Association and emphasized the importance of carrying out out-of-competition drug tests in a sport rocked since last summer by marijuana use among wrestlers.

"I felt at the meeting that reform (of the sport) is not easy, but the focus of attention right now is on marijuana, and what's important is to carry out tests as early as possible," Shionoya told reporters.

He said he plans to meet soon with Japan Sumo Association Chairman Musashigawa to convey the same message.

The drug-use scandals came as the sport struggles to restore its reputation.

Top-division Russian grappler Wakanoho was arrested on charges of marijuana possession last August. Two other Russians tested positive in subsequent drug tests conducted by the sumo association, but calls for fresh tests were prompted by the arrest in January of second-division Japanese wrestler Wakakirin.