Japanese prosecutors arrested two officials at a sponsor of the Tokyo Olympics on Tuesday as part of a widening bribery investigation that media said involved a former member of the Tokyo 2020 board.

The Nikkei newspaper reported that publisher Kadokawa Corp paid 70 million yen ($498,000) to a company linked to the then Tokyo 2020 board member Haruyuki Takahashi, whom prosecutors suspect of helping the company become a sponsor of the Tokyo Olympics.

Kadokawa confirmed that prosecutors had arrested two officials at the company and raided its office on Tuesday over bribery allegations.

"The company will continue to fully cooperate with the authorities' investigations," it said in a statement.

It declined to comment on details of the matter because of the investigation.

Shares in Kadokawa ended the day 5.42% lower.

Takahashi is already in custody after being arrested last month on suspicion of bribery surrounding the Games. Media reported that prosecutors decided to re-arrest Takahashi, meaning he is facing longer detention so prosecutors can question him further.

Another Tokyo Olympics sponsor, Aoki Holdings, said on Tuesday that prosecutors had indicted two former executives and an executive on bribery charges.

They were arrested last month along with Takahashi following reports that he received bribes from Aoki, a clothing retailer.

The former chairman of Aoki, Hironori Aoki, told prosecutors he gave cash to the head of the Games' organising committee, former prime minister Yoshiro Mori, the Sankei daily reported last week.

Reuters has not able to contact Aoki for comment. The Tokyo District Public Prosecutors Office declined to comment.

Reuters was not able to reach Mori or his legal representative for comment. Mori denied receiving the cash to the Sankei, the newspaper reported.

Reuters reported in 2020 that Takahashi, who was paid millions of dollars to work on Tokyo's successful bid for the Olympics, said he played a key role in securing the support of a former Olympics powerbroker who was later suspected by French prosecutors of taking bribes to help Japan's bid.

Takahashi told Reuters at that time his work included lobbying International Olympic Committee member Lamine Diack, to whom he gave gifts, including digital cameras and a Seiko watch. He said then that there was nothing improper with the payments he received or with the way he used the money.

Diack, once one of the most powerful people in athletics, was jailed in France in 2020 for corruption. He died last year at the age of 88.

($1 = 140.5700 yen)