French Rugby Federation President Bernard Laporte is being held for questioning by the French Financial Prosecution Office, it is being reported.
Laporte, who is also the World Rugby vice chairman is being held for questioning amid ties with Montpellier owner Mohamed Altrad as part of an investigation into influence-peddling and illegal acquiring of assets.
The reports say four other people have also been detained for questioning - Altrad, 2023 World Cup chief organiser Claude Atcher, and FFR officials Serge Simon and Nicolas Hourquet.
Laporte is alleged to have pressured the French League's appeal committee into softening a sanction against Top 14 team Montpellier. A company he owns signed an image rights deal with the Altrad Group in 2017.
Altrad is now the sponsor of the French national team, of whom Laporte is a former head coach.