French investigators think the vote to give Rio the 2016 Olympic Games may have been rigged, it is claimed.
A Brazilian businessman paid $1.5m to the son of an influential International Olympic Committee member just days before the host city was chosen, according to French newspaper Le Monde.
"The French justice suspects that this money may have been used to influence the votes," it says.
Rio 2016 organisers say the vote was "clean".
The Brazilian city won the right to host the Games by 66 votes to 32.
The newspaper says investigators have established that a holding company belonging to the businessman paid the money to a company set up by Papa Massata Diack, a marketing consultant who is banned for life from athletics for alleged corruption, and who is also wanted by Interpol.
Papa Diack is the son of former IOC member and president of athletics' governing body Lamine Diack, who is currently being held in France on corruption charges.
The Brazilian businessman named by the newspaper subsequently won a number of construction contracts with the state of Rio related to building infrastructure for the Games.
French prosecutors announced last year that they were widening their investigation into corruption in athletics to include the bidding and voting processes for the hosting of the 2016 and 2020 Olympics.