SPRINGFIELD - With little more than four months to go before he stands for re-election, Gov. Rod Blagojevich's administration took a significant hit Friday.

The torpedo, however, wasn't from his Republican opponent, state Treasurer Judy Baar Topinka.

Rather, fellow Democrat Lisa Madigan, who is the Illinois attorney general, released copies of a letter outlining her decision to turn over control of a hiring probe to federal prosecutors.

The blockbuster letter, written by U.S. Attorney Patrick Fitzgerald, publicly states for the first time that an investigation of the Blagojevich administration's potentially illegal hiring practices involves "multiple state agencies and departments."

And it adds that investigators have "developed a number of credible witnesses" as they conduct their sweep of the state's executive branch.

"The political fallout of this is huge," University of Illinois-Springfield political scientist Kent Redfield said.

Madigan said she released the letter to show she was ending her office's role in the investigation.

"We are coordinating with the U.S. attorneys to avoid the potential for inadvertent interference with each other's investigations," Madigan said in a prepared statement. "My top priority is that these matters are thoroughly and professionally investigated and I am confident that will be the result of this agreement."

Blagojevich, at an appearance in Pekin, refused to answer questions about the letter.

Spokeswoman Abby Ottenhoff issued a statement saying Blagojevich's own anti-corruption efforts uncovered misconduct by "some bad apples," and the findings were turned over to Fitzgerald. "We will continue pursuing those who would break the rules," she said.

Jay Stewart, head of the watchdog Better Government Association, scoffed at that, pointing out that Fitzgerald's letter says nothing to indicate Blagojevich helped uncover the allegations being investigated.

"They're not going to let the facts get in the way of good spin," Stewart said.

In the two-page letter written on June 20, Fitzgerald says the Federal Bureau of Investigation began looking into allegations of fraudulent hiring practices by officials within the Blagojevich administration about a year ago. A second probe was opened last summer, he added.

Fitzgerald said the investigation focuses on alleged illegal hiring practices and the preparation of fraudulent hiring documents.

While it is the first time Fitzgerald publicly has acknowledged the ongoing probe, Blagojevich has been dogged by reports in recent months focusing on alleged improper hiring activity within the executive branch.

The revelations, which the administration has denied, come after Blagojevich took office amid the scandals of his now convicted predecessor, Republican George Ryan.

During his 2002 campaign, Blagojevich pledged to clean up and reform state government.

In May, however, Lee News Service obtained a list of nearly 300 names of people who were hired for state jobs after Blagojevich took office. The list also contained the names of politically connected people who sponsored the people for the positions.

Earlier this week, the Associated Press reported the governor's office allegedly took an interest in the hiring of a Democratic congressman's son-in-law to be a state airplane pilot, despite lacking proper credentials.

Redfield said Fitzgerald's public acknowledgement of the investigation is significant because the governor and his aides can no longer downplay the seriousness of the ongoing probe.

"This raises it to a whole new level," Redfield said.

The Associated Press contributed to this report.