[Ashcroft said:] "The suggestion that Mr. Berg was in some way involved in terrorist activity . . . is a suggestion that we do not have any ability to support and we do not believe is a valid one."

Moussaoui and an acquaintance used an e-mail address or other computer identification traced to Berg, Justice Department officials said. The FBI concluded that Berg had been one of numerous victims of scam artists who were stealing e-mail addresses and passwords at the main campus of the University of Oklahoma, where Berg had been a student, several officials said.

Berg, 26, never met Moussaoui, who attended the school later, officials said.

Ashcroft said the theft of Berg's e-mail address was unremarkable. "It is not uncommon for individuals from time to time to allow . . . computer use by other individuals in university settings," Ashcroft said.

Iraqi police arrested Berg in the northern city of Mosul on March 24. Maj. Gen. Mohammed Barhawi, the police chief in Mosul, said Thursday that Berg aroused suspicion because he was not carrying identification, according to National Public Radio. Two associates of Berg said this week, however, that he told them he had been carrying his U.S. passport and that police became suspicious because the passport contained an Israeli stamp.

Barhawi said the FBI asked the police to keep Berg in custody while its agents reviewed the case.

FBI agents questioned Berg on March 25 and 26 and a third time about a week later. He later told a friend that he was asked about terrorism.

FBI officials said Friday that the timing of the March interviews was a coincidence and did not affect the length of Berg's stay in Iraqi custody. It remains unclear why he was held for 13 days.

On April 5, Berg's parents filed a petition in U.S. District Court in Philadelphia, asserting that the U.S. military was illegally detaining their son. They contended that his detention prevented him from returning to the United States on March 30, as he had planned.

Berg was freed April 6 and returned to Baghdad that day. He vanished April 10 after leaving his hotel. His body was found Saturday, and a video depicting his slaying was posted on the Internet on Tuesday. He was buried Friday in a family plot in Jenkintown, Pa., near Philadelphia.

The Internet video attributed Berg's killing to Abu Musab Zarqawi, a Jordanian who U.S. officials believe is linked to al Qaeda. CIA officials said Thursday that they had performed a technical analysis of the video and concluded "with high probability" that the speaker on the video was Zarqawi, and that Zarqawi was the person shown decapitating Berg.