Apple Computer has warned it will likely have to revise its financial results since 2002 after a probe found stock option irregularities.
Apple is investigating the stock options given to boss Steve Jobs
The firm admitted its ongoing internal investigation had found mistakes in the way staff were awarded Apple shares.
Apple is also to delay its results for its past quarter ending 1 July.
It has not given any details of what the mistakes were, but analysts suspect Apple may have back-dated some stock options to make them more valuable.
Apple's investigation has uncovered questionable stock options issued between 1997 and 2001, one of which was made to its boss Steve Jobs.
While it said it was too early to say which quarters would need to be restated, it admitted that all financial statements from 29 September 2002 should "not be relied upon".
It said its latest financial results would be published when the probe was completed, but that it did not have a timescale.
Apple is expected to announce details of its latest computer operating system later this month.
The company's shares fell $1.29, or 1.8%, to $68.30 in New York.