Japanese Olympic Committee (JOC) president Tsunekazu Takeda, who also led the Tokyo bid, was among those quizzed in recent weeks at the request of French investigators, the Yomiuri Shimbun reported.
French authorities said in May last year that they were investigating the 2.8 million Singapore dollar (1.8 million euros, $2 million) payments to a Singapore-based consultancy.
Japanese officials have consistently denied wrongdoing and have said that the payments were for consulting services.
"Having no recognition of the violation of laws nor bribery, I have told (prosecutors) the same explanation I've given (previously)," Takeda told the Yomiuri. Private broadcaster Nippon TV carried a similar story.
A JOC investigation reported last September that it had found no evidence of bribery by Japanese officials in the case.
Diack, whose son Papa Massata Diack has denied receiving the money, was an International Olympic Committee (IOC) member at the time of the Tokyo bid.
"The Tokyo 2020 Organising Committee has no means of knowing the bid committee's activities," the organising committee said in an email to AFP.
Allegations the payments were improper were first reported by Britain's Guardian newspaper in last May. Tokyo beat Istanbul and Madrid for the right to host the 2020 Games.
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