Bookseller Barnes & Noble Inc. (BKS) said Tuesday it has received a subpoena from the U.S. attorney for the Southern District of New York, requesting documents regarding stock option practices.

Barnes & Noble has become one of more than 80 companies to say it is being investigated in a quickly spreading scandal over stock options.

The operator of the bookstore chain said it received the subpoena on Friday, making the statement in a brief regulatory filing. It had previously announced it was reviewing stock option practices and said the U.S. Securities and Exchange Commission was conducting an informal inquiry with respect to them.

Barnes & Noble said it is cooperating fully with the SEC and intends to cooperate fully in responding to the subpoena.