Several people have been held for questioning in relation to an investigation into France international Andre-Pierre Gignac's transfer to Marseille in 2010, reports Reuters.
Judicial sources -- who spoke to Reuters on condition of anonymity -- confirmed that a dozen people including agents as well as individuals close to the Marseille mob were being held.
OM president Vincent Labrune had been held for questioning last November as well as former club presidents Pape Diouf and Jean-Claude Dasier, with investigators seeking to discover whether any club officials took illegal commissions from Gignac's move from Toulouse.
Gignac's fine form this season earned him a recall to Didier Deschamps' France national team in October, with Marseille currently second in Ligue 1 behind table-toppers Lyon.
Deschamps denied any involvement in transfer dealings during his spell as coach at Marseille.
Gignac hinted in December that he would welcome a summer move to Inter Milan, saying: "I think I will leave at the end of the season... Inter is an institution. [Roberto] Mancini is a great coach. It would be great."