The Tokyo Olympic bid committee transferred a total of over 1.1 billion yen ($10.5 million) to overseas destinations around the time the Japanese capital was picked as the host city in 2013, sources close to the matter said Tuesday.

The sum includes the some 230 million yen paid to Black Tidings Co., a now-defunct consulting firm based in Singapore recently found to have transferred funds to the son of a one-time influential International Olympic Committee member in July and October 2013. Tokyo was chosen as the host city for the 2020 Olympics in September 2013.

With the exception of Black Tidings, other payees and specific amounts have not been disclosed due to confidentiality agreements, according to a member of the bid committee at the time.

Transfers to other destinations were also concentrated around the time before and after the Japanese capital was picked as the host city. According to the sources, there are also other cases of hundreds of millions of yen flowing to and from unknown destinations.

"We can surmise that (the payments) were for overseas consulting fees and hotel costs, but in order to foster a good environment for next summer's games more clarification and transparency is necessary," an expert on bidding said.

According to a report released by the bidding committee in April 2014, which covered the period from September 2011 to September 2013, bidding costs totaled 8.9 billion yen. This was made up of 5.4 billion yen paid by the committee using donations and other funding from private companies, and 3.5 billion yen covered by the Tokyo metropolitan government.

A discrepancy was found in the amount reported for overseas consulting fees, which the report said amounted to 780 million yen. According to an external investigative team of the Japanese Olympic Committee, overseas consulting fees were at least 1.1 billion yen.

The bidding committee also made around a dozen transfers totaling some 900 million yen to a company headed by Haruyuki Takahashi, a member of the Tokyo Olympic organizing committee's executive board and a former senior managing director at Japan's largest advertising agency Dentsu Inc., which was involved in the bidding process.

Despite the enormous sum, individual transfers like these were also not included in the report.

According to a review of documents leaked to the International Consortium of Investigative Journalists, of which Kyodo News is a member, the Black Tidings bank account had been dormant until the company received payments from the Tokyo bid committee.

The documents showed that the consulting firm had transferred some $370,000 to Papa Massata Diack, whose father Lamine Diack was a member of the IOC said to have influence over African votes at the time of the Tokyo bid. The 87-year-old Senegalese businessman held the top post at the global athletics' governing body from 1999 to 2015.