Apple has confirmed that US regulators investigating its stock options backdating case have informally requested more information from the company.

The company filed a statement with the US Securities and Exchange Commission (SEC) confirming the news late last week, Reuters reports.

Apple has already supplied the findings of its own internal enquiry to the SEC and the US Attorney's Office, and said it plans to continue full cooperation with the investigators.

The company warned that resolving the situation will be time-consuming, costly and "will distract management from the conduct of the company's business".

In its recent form 10Q filing with the SEC, Apple warned that: "Recent accounting regulations requiring the expensing of stock options have resulted in increased stock-based compensation expense, which may cause the company to reduce the amount of stock-based awards issued to employees. There can be no assurance that the company will continue to successfully attract and retain key personnel."