Serge Dassault, the billionaire manufacturer of French fighter jets, was in custody for alleged vote-buying in Corbeil-Essonnes, east of Paris, where he was formerly mayor.
The move comes a week after Dassault’s parliamentary immunity was lifted, reports AFP news agency.
Dassault was interrogated on Wednesday in the western Paris suburb of Nanterre, a judicial source said.
The judges suspect Dassault of operating an extensive system of vote-buying which influenced the outcome of three mayoral elections in Corbeil in 2008, 2009 and 2010, which were won either by Dassault or by his successor and close
associate Jean-Pierre Bechter.
The result of the 2008 vote, won by Dassault, was invalidated by the Council of State after the body which oversees public administration discovered a series of payments which could have influenced the outcome of the election.
That ruling did not require the same burden of proof as a criminal prosecution for vote buying would, but formal charges against Dassault now look inevitable.
Bechter has already been charged, as has Cristela de Oliveira, a former official in the mayor’s office who is suspected of allocating council flats to families in return for backing Dassault or Bechter.
As well as the alleged vote-buying, Dassault could be charged with money-laundering and misuse of public assets, sufficiently serious crimes to raise the possibility of a prison term.
In 1998, Dassault received a two-year suspended prison sentence in Belgium for bribing members of the country’s Socialist Party to win an army-helicopter contract in what became known as the Agusta scandal.