Prosecutors are now following up on media reports that allege Diak and one of his sons served as intermediaries between the Olympic host cities and members of the International Olympic Committee (IOC).
The IAAF has no say in who hosts the Olympics, but the Guardian newspaper reported that Lamine Diack and one of his sons, Papa Massata Diack, may have helped secure the 2016 games for Rio de Janeiro and the 2020 games for Tokyo.
Lamine Diack had initially supported Istanbul's bid for the 2020 games, but he appears to have changed his mind after a Japanese sponsor signed a contract with the IAAF. Papa Massata Diack had worked on Qatar’s bid to host the 2016 games.
Rio was awarded the Olympics in 2009 and Tokyo in 2013.
An official from the French prosecutor’s office said that these elements are being investigated, “but at this stage it is a question of verification. Nothing has been proved".
The IOC said it would act on any evidence uncovered by the prosecutors, but a spokesperson said that “at the moment, there is nothing to act on”.
Rules governing bids were tightened after a corruption scandal involving the 2002 Winter Olympics in Salt Lake City. Ten IOC members resigned or were expelled for bribery.
French prosecutors opened an investigation in December into the awarding of the 2021 World Athletics Championships to the US City of Eugene, Oregon, headquarters of the athletics brand Nike.
New IAAF president Sebastian Coe stepped down from his role as a Nike ambassador in December after he was accused of lobbying Lamine Diack to award the championships to that city.
France has been involved in the IAAF investigations since November, when evidence from a Lyon-based commission of the World Anti-Doping Agency revealed a state-sponsored culture of doping in Russia, and Lamine Diack was connected with taking millions of euros in bribes from Russian athletes and officials to cover up failed drug tests.
He is out on bail, having been charged with corruption and money laundering. Papa Massata Diack is wanted by France, and there is an Interopol arrest warrant out for him, on charges that he blackmailed athletes who failed drug tests.