The Japan Sumo Association says it will look into allegations that Yokozuna grand champion Harumafuji assaulted a junior wrestler.
Rank-and-file wrestler Takanoiwa is sitting out of the current 15-day Grand Sumo Tournament that began last Sunday in Fukuoka, western Japan.
He submitted a doctor's report on Monday recommending 2 weeks of treatment for a fractured skull, concussion and other injuries.
Several sumo association sources are saying that Harumafuji struck Takanoiwa's head with a beer bottle during a regional tour. The incident reportedly took place on October 26th during a gathering of wrestlers from Mongolia.
Association officials plan to interview the stable masters of the wrestlers involved, to verify what happened.
Yokozuna Harumafuji has offered his apologies.
Harumafuji told reporters on Tuesday morning that he is deeply sorry for causing trouble to Takanoiwa's stable master, members of his support group and the sumo association.
But he said he will not respond to questions about the alleged assault until after he consults his stable master.