Brooks said it is cooperating fully with the SEC in this matter.

The company also said it faces possible de-listing from the Nasdaq Marketplace for failing to file its most recent quarterly report in a timely matter. Brooks has received notice from Nasdaq that it will be de-listed at the opening of business May 23 unless it requests a hearing on this matter, the company said.

Brooks has said it would hold off on filing its most recent quarterly report, for the quarter ended March 31, pending its own internal investigation into past stock options granting practices.

Brooks said on Thursday that it would re-state quarterly financial results for 28 consecutive quarters from fiscal 1999 through fiscal 2005 due to concerns of improper stock option accounting.

Brooks is one of several companies to be ensnarled in a controversy over suspected "backdating" of stock options, a tactic that would increase the value of stock options awarded to executives by retroactively granting them at a time when a company's share price is relatively low. This issue was first brought to light in a March 18 article in the Wall Street Journal.

In recent weeks, chip makers Vitesse Semiconductor Corp. and Power Integrations Inc. and Altera Corp. have all announced that they are reviewing historical stock options granting practices in the wake of the Wall Street Journal article. Contract manufacturing services provider Jabil Circuit Inc. announced earlier this month that the SEC was conducting an informal inquiry into its options granting practices.

Several non-electronics companies, including UnitedHealth Group Inc., are facing inquiries into stock options granting practices.

Brooks announced in April that its board created a special committee comprised of independent directors to conduct an internal review of matters related to past stock option grants, including the timing of such grants and associated documentation. Brooks said Thursday that the special committee's investigation is not complete.