French judges investigating corruption in athletics have extended their inquiry into the conditions under which the 2016 and 2020 Olympic Games were awarded.
"We are looking at these elements, but at this stage it is a question of verification. Nothing has been proved," said an official from France's financial prosecutor's office.
Allegations of corruption in athletics which emerged last year have so far been focused mainly on events organised by the International Association of Athletics Federations (IAAF), which has no say in the awarding of Olympic hosting rights.
The French investigation was opened in December in response to media reports that questioned the way the IAAF awarded its 2021 championships to the United States City of Eugene.
World athletics has also been shaken in recent months by a wider corruption and doping scandal.
In response to the news, the International Olympic Committee (IOC) said it would act on any evidence French prosecutors provided about how the Rio de Janeiro 2016 and Tokyo 2020 games bid processes were conducted.
Spokesman Mark Adams said: "When we get evidence we have shown we will act on it. It is an easy thing to talk about, but no one has any evidence... At the moment there is nothing to act on."
Separately, the Rio 2016 organisers said there was no possibility the vote to award the games to the Brazilian city could have been tainted.
"Rio de Janeiro won the right to host the Games because it had the best project. The difference in the votes, 66 to 32 against Madrid, excludes any possibility of an election that could have been rigged," Mario Andrada, communications director for Rio 2016, told Reuters.
The IOC had to clean itself up more than 15 years ago when an investigation ahead of the Salt Lake City 2002 winter Olympics triggered the biggest corruption scandal involving IOC members. Ten of them resigned or were expelled in connection with bribery and rules governing bids were tightened.
In January two top Russian athletics officials and the son of former world governing body President Lamine Diack were banned from the sport for life for covering up an elite Russian athlete's positive dope test and blackmailing her over it.
The bans follow last year's World Anti-Doping Agency (WADA) independent commission report that found a state-sponsored culture of doping in Russia and prompted the country's suspension from the sport.