The EU executive said the probe would examine if Vivendi had started implementing the merger before getting a green light, and if it started divesting assets to seal the deal before the commission gave its needed approval for buyers.

The commission  announced it authorised the merger on June 9th, on condition that Vivendi sell its Editis publishing business and celebrity magazine Gala, because of overlap with Lagardere’s Hachette publishing unit and Paris Match magazine.

If Vivendi is found to have jumped the gun on the commission’s antitrust and merger rules, it could face fines of up to 10 percent of aggregated turnover.

“The European Commission has decided to open a formal investigation to determine whether, when acquiring Lagardere, Vivendi breached the notification requirement and ‘standstill obligation’ set out in the EU Merger Regulation, as well as the conditions and obligations attached to the Commission’s decision to clear the Vivendi/Lagardere transaction,” it said in a statement.

Vivendi said a probe was no indication of any wrongdoing and did not put into question the EU’s green light for the merger.

“At this stage, Vivendi has no details of this probe with which it plans to cooperate fully,” a statement said, insisting that it had “fully respected the applicable rules” and would continue doing so.

Media watchdog Reporters Without Borders, which had called for an investigation, said the launch of a probe was “excellent news”.