Attorney General Michael Mukasey named a prosecutor Monday to investigate whether former Attorney General Alberto Gonzales, other Bush administration officials or Republicans in Congress should face criminal charges in the firings of nine U.S. attorneys.

The launching of a criminal inquiry follows the recommendation of internal Justice Department investigators who concluded that, despite denials of the administration, political considerations played a part in the firings of as many as four of the federal prosecutors.

In their 358-page report, investigators said the lack of cooperation by senior officials at the White House and in the Justice Department left gaps in their findings that should be investigated further.

"Serious allegations involving potential criminal conduct have not been fully investigated or resolved," the report said, listing lying to investigators, obstruction of justice and wire fraud among the potential felony crimes.

Mukasey's appointment of Nora Dannehy, the acting U.S. attorney in Connecticut, to continue the inquiry leaves open the possibility that it won't be finished before President Bush leaves office in January.

Senators of both parties who led a congressional probe of the firings praised Mukasey's decision and cautioned Bush against pardoning anyone as he leaves the White House.

"The American people will see any misuse of the pardon power or any grant of clemency or immunity to those from his administration involved in the U.S. attorney firing scandal as an admission of wrongdoing," said Senate Judiciary Committee Chairman Patrick Leahy, D-Vt.

The report unsparingly criticized Bush administration officials, Republican members of Congress and their aides for the ousters, which touched off a scandal that stripped the Justice Department of its leadership and sparked a historic showdown in court.

The report by Justice Department Inspector General Glenn Fine and Office of Professional Responsibility Director Marshall Jarrett described Gonzales and his deputy, Paul McNulty, as "remarkably disengaged" from the process that led to the dismissal of the prosecutors.

Monday's report was the latest to criticize Gonzales' management of the Justice Department during his 31 months as attorney general. Gonzales quit under fire in September 2007.

In a statement issued by his attorney, Gonzales said: "My family and I are glad to have the investigation of my conduct in this matter behind us and we look forward to moving on to new challenges."

Gonzales' attorney, George Terwilliger, noted that the report found no unlawful conduct. "It seems rather odd," Terwilliger said, "that rather than bring the investigation to a close, the department would escalate the matter to the attention of a prosecutor."

U.S. attorneys are political appointees who serve at the pleasure of the president, but cannot be fired for improper reasons.

The report singled out the removal of U.S. Attorney David Iglesias in New Mexico — one of the nine — as the most troubling. A leading Republican political figure in New Mexico, Sen. Pete Domenici, had complained about Iglesias' handling of voter fraud and public corruption cases, and that led to his firing, the report said.

Iglesias, who now works as a paid speaker and practices law part-time, said he thinks criminal investigations should be pursued against Domenici and anyone else who may have broken federal criminal laws. He said he had not yet seen the report.

"I've said all along that these moves were improper and illegal and now it appears that they were criminal as well," he said in an interview. "Our complaints weren't just complaints of disgruntled former employees."

A spokesman for Domenici, who is leaving Congress at the end of the year, did not respond to requests for comment.

Investigators said their inquiry of the firing of Iglesias and others was hampered by the lack of cooperation from Domenici, former White House adviser Karl Rove, former White House counsel Harriet Miers, former Justice Department official Monica Goodling and other key witnesses.

The president's refusal to let Rove, Miers and White House Chief of Staff Josh Bolten testify before Congress about the firings touched off a legal fight that is now before a federal appeals court. Most recently a judge ordered Miers to answer questions from the House Judiciary Committee about the firings.

The report concluded that Gonzales' chief of staff, Kyle Sampson, was the person most responsible for developing the plan to fire the prosecutors and said that Sampson's comments to Congress, the White House and others were misleading.

Sampson and others claimed at first that the prosecutors' poor performance inspired their firings. But the report found that Bud Cummins, the U.S. Attorney in Arkansas, was forced out to make way for Timothy Griffin, who had previously been Rove's deputy in the White House political office.

It also said the dismissal of Todd Graves, the U.S. Attorney for the Western District of Missouri, probably resulted from pressure from the office of Republican Sen. Christopher "Kit" Bond. Bond was upset that Graves did not intervene in a dispute between the staffs of Bond and Republican Rep. Sam Graves, the prosecutor's brother, the report said.

A spokeswoman for Bond did not immediately return a call for comment.

Investigators found no evidence that Arizona U.S. Attorney Paul Charlton and U.S. Attorney Carol Lam of San Diego were fired for prosecuting Republican members of Congress.

Similarly, the report says Justice Department officials had legitimate concerns about the work of two other prosecutors who were fired — Margaret Chiara of Grand Rapids, Mich., and Kevin Ryan of San Francisco.