Sumo grand champion Hakuho was questioned by police in the city of Fukuoka on Tuesday as a witness of an alleged assault by fellow yokozuna Harumafuji on another wrestler at a bar in western Japan last month, investigative sources said.

The sources said Hakuho's account of the incident that occurred during a drinking session was similar to what Harumafuji had told the police. Hakuho told reporters after the questioning, "I told them everything that I know. I will now leave it up to the (sumo) association and the police."

The police have questioned Harumafuji on a voluntary basis as well as others who were present. They may refer Harumafuji to prosecutors by the end of the year on suspicion of assaulting lower-ranked wrestler Takanoiwa, the sources said.

The 33-year-old Harumafuji has admitted to striking Takanoiwa, 27, with his fists and a karaoke machine remote control at the bar in the city of Tottori in late October during a regional tour, according to the investigative sources.

Echoing Harumafuji's account, Hakuho was quoted as telling the police on Tuesday that he saw Takanoiwa hit "with a karaoke machine remote control," the sources said.

Other sources close to the matter said earlier that Harumafuji was angered by Takanoiwa attempting to use his smartphone while being scolded for his behavior by 32-year-old Hakuho, who also holds sumo's highest rank of yokozuna.

Hakuho's account of what transpired before the alleged assault was not immediately known.

Harumafuji was initially reported to have hit Takanoiwa with a beer bottle. But Hakuho told reporters shortly after the scandal surfaced that the claim about a beer bottle was inaccurate and he had quickly intervened to stop the fighting and took Harumafuji out of the private room where the three Mongolians were drinking with other wrestlers.

In Fukuoka, where Hakuho won his 40th title at the Kyushu Grand Sumo Tournament on Sunday, Japan Sumo Association Chairman Hakkaku pledged to sumo wrestlers that "problems of violence will never happen again."

The chairman addressed wrestlers from the upper ranks but Harumafuji and Takanoiwa were absent, according to the association.

Earlier in the day, Hakkaku apologized over the scandal to Japan Sports Agency chief Daichi Suzuki in Tokyo.

"I'm deeply disappointed. It is not what the public expects," Suzuki said.