The French competition authority began an investigation into certain activities of Adecco Group, ManpowerGroup Inc. (NYSE: MAN) and Randstad Holding NV. All three companies said they are cooperating with the investigation.

Adecco reported the investigation is in regards to alleged violations of French competition law.

Randstad said in a statement, “Randstad cannot give any further comments at this stage but Randstad cooperates openly with the authority and we are confident that the investigation will result in a positive outcome.”

The three companies rank as the largest staffing firms in France with Adecco holding 26 percent of market share, ManpowerGroup with 19 percent and Randstad with 14 percent, according to research by Staffing Industry Analysts.

Adecco, ManpowerGroup and Randstad were previously fined by the French competition council in 2009. Adecco was fined €34.2 million (US$43.8 million), ManpowerGroup fined €42.0 million (US$53.8 million) and Randstad fined €18.2 million (US$23.3 million). The 2009 fines resulted from investigations of anti-competitive practices that took place between March 2003 and November 2004. The investigations included Adecco, ManpowerGroup and Vedior (which was later acquired by Randstad).