The Rio 2016 organising committee has denied claims that it relied on bribes to secure the Olympic Games hosting rights.
A report in France's Le Monde newspaper on Friday claimed that Brazilian businessman Arthur Cesar de Menezes Soares Filho paid $1.5 million to Papa Massata Diack, the son of then-president of the International Association of Athletics Federations (IAAF), Lamine Diack, three days before the 2009 vote on the 2016 Games host city, reports Xinhua news agency.
The newspaper also alleged that Papa Massata Diack paid around $300,000 to IOC member Frankie Fredericks before the vote. Fredericks has denied any wrongdoing.
An IOC spokesperson said on Friday that its commission is probing the claims.
Rio 2016 communications director Mario Andrada said Rio won the Olympic hosting rights in a transparent vote.
"Rio's victory was very clear," Andrada said. "The French investigation concerns six members of the IOC and six members would not have changed the result at all. The vote was clean."
Madrid won the initial ballot but Rio was declared the winner by a 34-vote margin in a third-round poll of IOC delegates.
Fredericks said he received the cash in question for work to promote athletics in Africa.
"The payment has nothing whatsoever to do with the Olympic Games," said Fredericks, now an IAAF council member.
"I was not an IAAF board member at the time and did not breach any regulation or rule of ethics," he told Le Monde.