French carmaker Renault said Wednesday that a joint Renault-Nissan audit of their Dutch subsidiary RNBV had raised "serious questions" over millions of euros in expenses incurred by ousted CEO Carlos Ghosn.

"Certain expenses which have yet to be precisely quantified, but may amount to several million euros since 2010, raise serious questions as to their conformity with RNBV's corporate interest," Renault's board of directors said in a statement.

The statement said "RNBV's internal organisation suggests serious deficiencies in terms of financial transparency and expenditure control procedures."

The board had asked Renault's management to work with Nissan "to jointly remedy these deficiencies as soon as possible," it added.

The statement came amid reports in Japan that prosecutors there were considering bringing further charges against Ghosn, who spent more than three months in custody on allegations of financial misconduct involving his pay and Nissan's accounts.

The reports said the investigators were reportedly eyeing a possible aggravated breach of trust charge related to at least $32 million in Nissan funds transferred to a distributor in Oman.

The transactions reportedly involved Renault and Nissan's Amsterdam-based venture RNBV.

Some of the money is believed to have been used to buy a yacht allegedly used by Ghosn, 65, and his family, according to a source familiar with the matter.

In a stunning development that rocked Japan and the business world, Ghosn was arrested on November 19 off his private jet at a Tokyo airport and taken into custody.

Nissan swiftly removed him as chairman and he was also later deposed as chairman and CEO of Renault.

Ghosn spent more than 100 days in detention with limited access to lawyers before being released on a bail of nearly USD 9 million last month.

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