It is not clear what happened to the law firm’s findings after it delivered its report. But shortly after, Motoo Nagai, a Nissan director who heads the company’s audit committee , told Ms. Murray that she could no longer participate in any investigations involving Mr. Nada, according to an email reviewed by the Times . She subsequently resigned. Her last day in the office was Aug. 30, and she officially left the company on Sept. 9 . She had planned to present the results of her yearlong investigation to the full board that day, said the people familiar with the plans .

Mr. Nagai has told reporters that Ms. Murray had been contemplating resigning since July and that the timing was coincidental. The company has said she resigned for personal reasons.

The board’s meeting on Sept. 9 focused on Hiroto Saikawa, Mr. Ghosn’s successor as chief executive. The board unanimously asked for his resignation, and he resigned that day. He had admitted earlier that month that he received about $440,000 in improper share-based compensation. Mr. Saikawa said he had not realized that the overpayment was “against the rules” and vowed to return the money.

But some directors at the meeting demanded more information about the compensation of other executives and were growing frustrated with a lack of it, said people who were there . Days before, Bloomberg News reported that Mr. Nada had received overpayments, without specifying the amount or how. Jean-Dominique Senard, the chairman of Nissan’s French partner, Renault , and other board members asked why they were learning about top executives’ pay issues from media reports.

In its statemen t, Nissan said the law firm’s findings had been “reflected” in a broader report shared with the board after the meeting. But that broader report named only directors, not executives , who received improper compensation, according to people aware of its contents . It did not identify the executives, like Mr. Nada, who received that compensation nor say how much they received or how they received it, the people said. Some members of the board were not aware that the firm had been hired, they said.