Apple has found more problems with its accounting for stock options grants and now says it is likely to restate some past financial results.

The company said last month that an internal investigation had uncovered problems with some stock option grants made between 1997 and 2001. On Thursday, it said it had found additional evidence of irregularities. Because of the new discoveries, Apple is likely to have to restate past financial results to record non-cash charges for the expense of making stock option grants, the company said in a statement on Thursday. Apple also said it filed a Form 8-K to the US Securities and Exchange Commission (SEC) that said its earnings, press releases and similar communications for periods after September 29, 2002 should not be relied upon.

Because of the ongoing investigation, the company also will delay the filing of its Form 10-Q for the quarter ended July 1 to the Securities and Exchange Commission (SEC), Apple said. Form 10-Q is a formal report of quarterly results. The Cupertino, California, company plans to file the 10-Q and any restated results as soon as possible after the investigation is finished, it said.

On June 29, Apple said it had found problems with historical stock options grants, including one to CEO Steve Jobs. The grant to Jobs had been cancelled and Jobs didn't financially benefit from it, according to Apple. At that time the company said it was hiring outside counsel to investigate and had informed the SEC.

In recent months, a long line of high-tech companies have run into problems with how they accounted for stock-option grants to employees and executives. Options were a critical form of currency in Silicon Valley during the tight job market early in this decade.

In after-hours trading on Thursday, Apple's stock was down $3.59 to $66.00.