Nissan Motor Co. and Renault SA have hired the French auditor Mazars to investigate possible wrongdoing within their automotive alliance, people familiar with the matter said, a sign the partners are moving forward on a joint probe following Carlos Ghosn's arrest for alleged financial crimes.

Mazars will look into Renault-Nissan BV, the Amsterdam-based unit set up by the carmakers to coordinate their alliance, for any misconduct such as the misuse of company assets, the people said, asking not to be identified as the matter is private. Spokesmen for Renault, Nissan and the alliance declined to comment. Mazars didn't return calls seeking comment.

The audit follows the arrest of Ghosn in Tokyo late last year on allegations of understating his income at Nissan by around ¥9 billion and temporarily transferring personal trading losses to the company. The auto-industry luminary, who has denied wrongdoing, has been in custody ever since.