U.S. Attorney Patrick Fitzgerald says the corruption charges against Illinois Gov. Rod Blagojevich represent "a truly new low."

At a news conference in Chicago on Tuesday, Fitzgerald called it a sad day for the citizens of Illinois.

Also, the head of the FBI office in Chicago, Robert Grant, says if Illinois isn't the most corrupt state in the United States, it's a strong competitor.

Blagojevich was arrested hours earlier on charges that accuse him of trying to benefit from his ability to appoint President-elect Barack Obama's replacement in the U.S. Senate.

A 76-page FBI affidavit says the 51-year-old Democrat was intercepted on court-authorized wiretaps over the last month conspiring to sell or trade the vacant Senate seat for personal benefits for himself and his wife, Patti.

Fitzgerald says federal investigators bugged Blagojevich's campaign offices and placed a tap on his home phone.

Fitzgerald said, "We make no allegations" that Obama was aware of any alleged scheming by the Illinois governor.

The governor has repeatedly denied any wrongdoing.

Grant, the FBI chief, says even seasoned investigators were stunned by what they heard on those tapes.

Fitzgerald described the situation by saying: "We were in the middle of a corruption crime spree and we wanted to stop it."