French Rugby Federation (FFR) president Bernard Laporte was questioned for a second day in police custody on Wednesday as part of an investigation into suspicions he favoured Top 14 club Montpellier, a source close to the case said.
Montpellier's billionaire owner Mohed Altrad and the chief organiser of the 2023 Rugby World Cup to be held in France, Claude Atcher, are also in custody, along with two senior FFR officials.
Laporte, 56, a former coach of the France national team who is also vice-chairperson of the game's global body World Rugby, is suspected of pressuring the appeals committee of the French league to reduce a disciplinary punishment against Montpellier in 2017.
Laporte is standing for re-election as FFR president with the result expected on 3 October. On Tuesday he called the timing of the legal proceedings "revolting" and claimed he was the victim of a putsch attempt.
"It's a true attempt at a coup of which there is no doubt about the motivation of the creators. It all adds up to a truly foul electoral strategy," Laporte said in an open letter to clubs.
He has always denied intervening in favour of Montpellier but admits he had a telephone conversation with the head of the appeals committee, Jean-Daniel Simonet, before the decision was changed.
Inspectors at the sports ministry established that the committee's decision was "modified" in June 2017.
In France, suspects can be detained for up to 48 hours. After that period the Financial Prosecution Office can decide whether to continue the preliminary investigation, to open a judicial inquiry, or to end the investigation. In the latter case, it can choose to close the file without prosecution or to send the suspects to trial.