TOKYO • Officials who led Tokyo's successful bid to host the 2020 Olympics have been cleared of any illegal activity by a Japanese investigation, following revelations that the city had paid S$2.8 million to a company linked to the son of the disgraced former world athletics chief Lamine Diack.

A report published yesterday by an independent panel appointed by the Japanese Olympic Committee said the payment to Black Tidings, a Singapore-based consultancy, was legitimate and had been made in return for consulting services.

"I believe that Tokyo has been cleared of any suspicion of bribery" in connection with its winning bid, said Yoshihisa Hayakawa, a lawyer who led the three-member panel.

The Guardian revealed in May that French authorities were investigating suspicious payments to Black Tidings, whose president, Ian Tan Tong Han, is a close friend of Papa Massata Diack.

Diack's father was an influential member of the International Olympic Committee (IOC) when it awarded the 2020 Games to Tokyo in September 2013.

The same Singapore-based account was also used to transfer funds in the attempted cover-up of a Russian doping case, according to the World Anti-Doping Agency (Wada).

Prosecutors in France are now conducting an investigation into whether the money led to the elder Diack.

The younger Diack, who is wanted in France on alleged bribery, money laundering and corruption charges - which he has denied - was employed by the IAAF, the world athletics governing body, as a marketing consultant, French prosecutors said.

The 50-page English version of the Japanese Olympic Committee report said there was no evidence that the consultancy arrangement between the Tokyo 2020 bid committee and Tan was "illegal or invalid under the civil laws or criminal laws of Japan, and there is no doubt that it is lawful".

The report said there was no way any members of the Tokyo bid committee could have been aware that Tan and Papa Massata Diack were friends.

In fact, Tan and Diack have been close since they met at the Beijing Olympics in 2008, with Tan even naming his child, born in 2014, Massata, according to Wada's investigation into the Russian doping scandal.

Hayakawa acknowledged that the panel were disappointed that they had been unable to question Tan or either of the Diacks during its investigation.

"I am personally very disappointed that, despite initial indications by their lawyers that a meeting was possible, we were not able to interview the Diacks," the lawyer said.

"If we could have met Tan, especially, I'm sure we could have examined what exactly happened in this case.

"I am still holding out hope that we can eventually speak to all three of them."

The Japanese investigation was also unable to study official committee documents because they had been destroyed after Tokyo was chosen to host the 2020 Games.

Tokyo beat Istanbul and Madrid in the race to host the Summer Games in the vote held in Buenos Aires in 2013.

THE GUARDIAN, AGENCE FRANCE-PRESSE