(CNN) - The U.S. Attorney's Office in Chicago, said Thursday it would release news late in the afternoon about a "significant criminal matter" that would include a court filing.
A written statement gave no information on what the subject might be, but on January 5 federal Judge James Holderman gave the office three additional months to decide whether to indict then-Gov. Rod Blagojevich, who was impeached and resigned from office. That deadline ends Sunday.
The U.S. Attorney's Office said its announcement would be made in a news release, and posted on its Web site.
Blagojevich was arrested in December on federal corruption charges that included allegedly trying to sell President-elect Barack Obama's vacant Senate seat.
The Illinois House of Representatives voted overwhelmingly in January to impeach the Democrat, accusing him of abusing his gubernatorial power.