By Kasper Jade

Published: 05:00 PM EST

Apple Computer on Wednesday said an investigation by a special committee of outside directors discovered 15 dates between 1997 and 2002 in which stock option grants to executives or board members listed dates that precede the approval of those grants.

The iPod maker initiated the independent investigation in June after a management review discovered irregularities in past stock option grant practices, including one questionable grant to its CEO.

During the three-month probe, Apple said the committee of outside directors, together with independent counsel and accountants, examined more than 650,000 emails and documents, and conducted interviews with more than 40 current and former employees, directors and advisors.

In statement issued by the Cupertino, Calif-based company at close of the stock market, it said the investigation found no misconduct by any member of Apple's current management team and found the most recent evidence of irregularities relates to a January 2002 grant. However, it reported that option grants made on 15 dates between 1997 and 2002 "appear to have grant dates that precede the approval of those grants."

In a few instances, Apples said, chief executive Steve Jobs was aware of the backdating, but he "did not receive or otherwise benefit from these grants and was unaware of the accounting implications."

Apple also said the investigation raised serious concerns regarding the actions of two former officers in connection with the accounting, recording and reporting of stock option grants. Details regarding their actions will be provided to the SEC, it said.

"I apologize to Apple's shareholders and employees for these problems, which happened on my watch. They are completely out of character for Apple," said Jobs. "We will now work to resolve the remaining issues as quickly as possible and to put the proper remedial measures in place to ensure that this never happens again."

Apple said its independent auditors are reviewing the findings of the independent investigation, but management and the audit committee continue to believe the company will likely need to restate its historical financial statements to record non-cash charges for compensation expense relating to past stock option grants. 

"The company and its independent auditors are reviewing recent accounting guidance published by the SEC, and have not yet determined the amount of such charges, the resulting tax and accounting impact, or which periods may require restatement," Apple said. "The company continues to proactively inform the SEC of its findings."