TOKYO  — Fresh off a gambling scandal that deeply sullied its image, Japan’s national sport of sumo wrestling is now grappling with allegations that senior wrestlers and coaches used cell phones to plan how to fix bouts.

Police have found text messages on confiscated mobile phones that implicate as many as 13 wrestlers in schemes to fix matches, the Japan Sumo Association and Japanese media said Wednesday. One reportedly went into detail about how he would attack and how he wanted his opponent to fall.

The text messages, found on the phones of a wrestler and a coach, indicate that the wrestlers routinely fixed bouts and charged hundreds of thousands of yen (thousands of dollars) per match to do so, according to Japan’s Kyodo news service.

Public broadcaster NHK, which airs the six annual sumo tournaments live, said the messages hinted at one bout going for as much as 500,000 yen ($5,000). It said the messages referred to wrestlers "owing each other wins," and appeared to show a repeated pattern of cheating.

Top sumo officials held an emergency meeting Wednesday to discuss the reports.

"I deeply apologize to the fans," said Japan Sumo Association chairman Hanaregoma. "It will take some time to get to the bottom of this and we request that you be patient."

He said any violations would be dealt with sternly.

Yoshiaki Takaki, Minister of Education, Culture, Sports, Science and Technology, said he has instructed the sumo association to investigate.

"The sumo association has already had a series of major problems," he said. "It’s a serious problem if the latest case turns out to be true."

Police had no immediate comment. It was not clear if a formal criminal investigation would be launched or if the matter would be dealt with as an internal issue by the sumo association.

Sumo — which has its roots in ancient religious purification rituals — has been dogged by scandals over the past few years and has seen its popularity nosedive.

Several wrestlers were arrested last year for betting illegally on baseball games, allegedly with gangsters as go-betweens. That scandal followed allegations in 2009 of widespread marijuana use among the ranks that led to the expulsion of three Russian fighters.

Hanaregoma said the text messages this time were found on phones confiscated when police were investigating the baseball gambling ring. Media reports said four wrestlers in the sport’s elite top division — including two Mongolians — were implicated.

Last week, reports surfaced that three sumo wrestlers were involved in drunken incidents, including a late-night brawl.

Scandals are particularly sensitive in sumo because it is seen by most Japanese as not only a sport but a bastion of Japanese tradition and culture. Wrestlers are expected to observe a high standard of public behavior.

But rumors of ties with the underworld have been rife, and the baseball gambling scandal deeply hurt sumo’s image.

Unsubstantiated allegations of gangster involvement in bout-fixing have plagued the sport for decades, but have never been proved. There were no immediate reports of gangsters mentioned in the text messages.