PARIS — The German auto giant Daimler said Thursday that French authorities have placed it under formal investigation as part of an inquiry into allegations of insider trading in the sale of shares in EADS five years ago.

The move forms part of a broader criminal inquiry by French investigative judges that in recent weeks has also targeted another major industrial shareholder of European Aeronautic Defense and Space — the French conglomerate Lagardère — as well as seven current and former executives of the group and its Airbus subsidiary.

“We think the whole process is unusual and not easy to understand,” said Florian Martens, a Daimler spokesman.

Under French law, being placed under formal investigation is one step short of criminal charges but can lead to an eventual trial.