TOKYO — Stung into action by the arrest of one of its top wrestlers, the tradition-steeped Japan Sumo Association conducted its first drug tests this week and two Russian wrestlers tested positive for marijuana use.

Both wrestlers on Wednesday denied they had used the drug.

The positive tests are the latest scandal to hit the ancient sport, which has been criticized for the bad conduct by some of its most senior athletes and a criminal investigation into abusive hazing at one of its training centers.

The Japan Sumo Association, which oversees the professional sport, said all 69 wrestlers in the top two divisions were tested Tuesday for marijuana and two kinds of stimulants.

The test was conducted in response to the arrest and subsequent lifetime ban last month on wrestler Wakanoho, who police claim had a small amount of marijuana in his wallet.

Wakanoho, who is Russian, was the first wrestler ever to be ejected from sumo for drug use.

The association announced that Russian wrestler Roho and his brother, Hakurozan, both tested positive for marijuana. They were the only wrestlers who tested positive, it said.

The association did not immediately announce any punishment for Roho or Hakurozan.

Roho, whose real name was listed by the association as Boradzov Soslan Feliksovich, is in sumo's top division, while Hakurozan — who was listed as Baradzov Batraz Feliksovich — is in a lower tier. Foreign wrestlers assume Japanese fighting names when they enter the sport.

"I have never used or even touched the stuff," Roho told reporters Wednesday. "I want another test to be conducted at a hospital I can trust."

Hakorozan made a similar denial, according to the Kyodo news agency.

Sumo, which has its roots in ancient religious ritual, is considered Japan's national sport, and its athletes and coaches are held to high moral standards in and out of the ring. Wrestlers wear their hair in traditional-style topknots, and make public appearances in kimono robes.

But the sport has been rocked by a series of scandals over the past year or so.

Last year, grand champion Asashoryu was given an unprecedented two-tournament suspension after claiming an injury and missing summer tour events, only to be shown later on television playing football in his native Mongolia.

In February, Japanese police arrested a former sumo trainer over the death of a 17-year-old wrestler after an alleged beating during training camp last June.

Drug violations are taken very seriously in Japan.

Under Japan's Cannabis Control Law, possession of marijuana is punishable by up to five years in prison. Foreigners convicted of drug crimes can also be deported and given a lifetime re-entry ban.

An association official, who spoke with The Associated Press on condition of anonymity, said the group is considering expanding its drug testing to include steroids. He said tests for marijuana and stimulant drugs will also likely be conducted more regularly.