The Department of Justice's inspector general has concluded that an FBI whistle-blower's allegations against a colleague in her office "were at least a contributing factor" in the firing of the whistle-blower, according to a letter to Congress by FBI Director Robert S. Mueller III.

Inspector General Glenn Fine also concluded that the FBI failed to "adequately pursue" allegations of espionage by whistle-blower Sibel Edmonds against the co-worker, a conclusion that prompted the FBI to review its handling of the allegations and conduct "additional investigation as appropriate," Mueller wrote.

Edmonds, a former translator in the FBI's Washington field office, has alleged that her co-worker attempted to censor translations of wiretapped conversations involving an unnamed group to which the co-worker belonged.

Mueller's letter said, however, that Fine "did not conclude the FBI retaliated against" Edmonds, a former translator under contract to the FBI's counterterrorism program. She is suing the government over her March 2002 dismissal.

The apparent conflict between that conclusion and the assertion that Edmonds was fired partly because of her allegations against another translator has prompted head-scratching at the FBI, said a senior bureau official, who asked not to be named because the case is being litigated and involves classified information. The bureau is "still trying to figure out" what Fine meant, he said.

Mueller's letter was written on July 21 and posted yesterday on the Internet by the Project on Government Oversight, a nonpartisan study group.

In the letter, Mueller, who has told lawmakers that whistle-blowers will be protected, promised that FBI officials will work with Fine to determine whether any agency employees should be disciplined. He said he plans to send a letter to employees reiterating "that I encourage them to raise good faith concerns about mismanagement or misconduct."

Mueller's letter, first reported in Thursday's editions of the New York Times, was written in response to congressional anger over the treatment of Edmonds, who is at least the third FBI whistle-blower to accuse the bureau of retaliation or interference since 2001. That year, Coleen Rowley, a legal counsel in the Minneapolis office, complained to Congress that her office had been blocked by senior officials from pursuing suspicions against terrorist suspect Zacarias Moussaoui.

In 2002, an FBI investigator in Washington, John E. Roberts, accused senior officials of trying to intimidate him for publicizing his concerns on "60 Minutes." Edmonds subsequently appeared on "60 Minutes" to voice her critique of the bureau, although it told her not to do so. She also testified in secret before the Sept. 11 commission.

"It is a vindication," Edmonds said yesterday. But she complained that the bureau "is not doing anything to fix these problems. On the one hand, they are asking the public to be more vigilant regarding this terrorist threat. On the other hand, they are not being vigilant within their own department."

Edmonds was born in Iran and reared in Turkey, and has Turkish citizenship. In addition to English, she speaks Farsi, Turkish and Azerbaijani. She has not publicly named the group wiretapped by the FBI but said her Turkish American co-worker attempted to recruit her into it. She has told her lawyer, Mark S. Zaid, that the FBI never interviewed her about the alleged attempted recruitment or spoke to a key witness.

Mueller's letter was sent to Senate Judiciary Committee Chairman Orrin G. Hatch (R-Utah) and two other committee members who have raised concerns about the FBI's response, Sen. Patrick J. Leahy (D-Vt.) and Sen. Charles E. Grassley (R-Iowa). All declined to comment yesterday. But a Senate official who asked not to be named said Mueller promised to arrange for Fine's report to be partially declassified and provided to Congress in that form.

Staff writer Dan Eggen contributed to this report.