The U.S. Attorney for the Northern District of California sent Marvell a grand jury subpoena demanding option grant documents, the company said in a regulatory filing Tuesday. The SEC sought similar documents, Marvell said.

Marvell is among at least 60 companies whose options grants to executives and directors are under scrutiny by the SEC, the Justice Department or internal probes. At issue is the timing of grants and their cost.

The investigation of corporate wrongdoing is the biggest since probes into illegal mutual-fund trading almost three years ago.

Shares of Marvell fell $3.79, or 8.5 percent, to $41.05 at 10:27 a.m. in Nasdaq Stock Market composite trading. The shares had declined 20 percent this year before Wednesday.

Marvell, which said last month it would buy Intel Corp.'s business that makes chips for the BlackBerry, Treo and Q handheld devices, said it plans to "cooperate fully" with the inquiries. Marvell said the SEC described its inquiry as "informal."

The company also said it has formed a board committee to conduct an internal review of options awards.