TOKYO — Sumo wrestlers with pot bellies, yes. Sumo wrestlers with pot? Now that's harder to grapple with.

In the past six months, four wrestlers have been kicked out of the ancient sport for allegedly smoking marijuana, creating the biggest drugs-in-sports scandal that Japan has ever seen.

Although three of the wrestlers who have been expelled from the sport were from Russia, the arrest last week of a 25-year-old Japanese athlete who goes by the ring name of Wakakirin for possession of marijuana has raised concern that use of the drug may be more widespread than originally thought.

In Japan, sumo wrestlers are not seen as athletes in the way that baseball or tennis players are. A photo of U.S. swimming star Michael Phelps with a marijuana pipe got wide play in the media here, but nowhere near the consternation of the sumo scandal.

The sting of the busts in sumo — which only recently introduced doping tests — was made all the worse because of the breakdown in Japan's still relatively drug-free environment. Marijuana use, in particular, is rising rapidly despite a stiff punishment — up to five years in prison for possession.

"We are appalled by his utter folly," The Asahi, a major newspaper, said in an outraged editorial. "Some young people casually try pot. It is vital that we educate them on the risks of this drug from a fairly early age."

More than being simply a drug issue, however, the scandal has been amplified by the fact that it involves one of the world's oldest and most tradition-bound sports — and one that is solidly rooted in religious purification ritual.

Sumo wrestlers are expected to live the old-school life of a disciple. They wear their hair in topknots, dress in traditional robes and train in communal "stables." Their schedules are tightly regulated and the word of their coaches, who are still called "masters," is absolute and final.

Sumo aficionados like to note that former grand champion Musashimaru, of Hawaii, had a 10 p.m. curfew.

But that is changing.

The wrestlers at the center of the scandal came from training stables where a new, and often younger, stable master was in charge, and discipline was not what it might have been in the old days.

"In the most recent cases, the normal connections are not there anymore," said David Shapiro, a sumo color commentator for broadcaster NHK. "Stable masters normally are your surrogate fathers and now they are your surrogate stepfathers. There are certain stables where this never would have happened."

Still, many Japanese believe that to stain the purity of sumo is to tarnish the heart of Japan itself.

Moving quickly to ease criticism, the Japan Sumo Association, which oversees the professional sport, voted this week to dismiss Wakakirin, whose legal name is Shinichi Suzukawa.

Many Japanese saw even that punishment as too light. Dismissal — unlike the harsher punishment of expulsion from the sport — leaves open the door for Wakakirin to receive severance pay, although the Kyodo news agency reported that he has opted not to do so.

"It is hard not to call them lenient in this case," said Sports Minister Ryu Shionoya. "This is utterly shameful."

Sumo initiated limited drug-testing in September after the Russian wrestler Wakanoho was caught by police for allegedly possessing marijuana. Two wrestlers, Roho and his brother, Hakurozan, also of Russia, tested positive and were kicked out of the sport.

All three were top-division wrestlers, and well-known in Japan even beyond sumo circles.

With Wakakirin's arrest, officials now say they will further beef up doping tests for marijuana and stimulants. Marijuana is not considered a performance-enhancing drug.

Wakakirin reportedly became interested in marijuana after reading about it in magazines and seeing others smoking it at hip-hop clubs.

Mark Buckton, a sumo columnist and blogger, said he thinks the scandal has pretty much run its course.

"A lot of these guys are young and single so it could go further, but it's not really fair to say it's a breakdown in discipline in sumo," he said. "There are 700 men in sumo and the majority of them don't smoke marijuana."

In sumo, competitors vie to push their opponents out of the ring or make them touch the dirt with any part of their bodies other than the soles of their feet. The wrestlers, who can weigh up to 550 pounds and are mostly in their 20s, fight in six 15-day tournaments each year.

Despite its status as Japan's national sport, sumo has been hit with several scandals in recent years, including persistent accusations of bout-fixing, the hazing death of a young wrestler two years ago, and the antics of its top champion, a fiery Mongolian who fights under the name of Asashoryu.

Asashoryu recently had to sit out three tournaments as punishment for skipping a road trip to go home to Mongolia. He claimed he had an injury, but was seen playing a spirited game of soccer in his homeland. Last month, after winning the most recent tournament, Asashoryu was warned by sumo officials for pumping his fists to celebrate.

Displays of emotion in the ring, which is considered sacred ground, are frowned upon.