Attorney General John D. Ashcroft said today that Nicholas Berg, the young American businessman who was beheaded in Iraq, had been investigated by the FBI two years ago on suspicion of a link to terrorists but had been absolved of any such connection.

Ashcroft vowed that the Justice Department would "work hard" to find Berg's murderers.

"This barbaric murder of Nicholas Berg illustrates the kind of evil that we face in the war against terror," he said. "And the United States will pursue his killers and we will bring them to justice."

He made the comments in a news conference at the Justice Department after Berg was buried this morning in a cemetery near his hometown of West Chester, Pa., in a private ceremony.

Berg, 26, was found dead Saturday outside Baghdad nearly a month after he disappeared while preparing to leave Iraq following an unsuccessful search for work. A video posted on an Islamic militant group's Web site Monday showed him being decapitated by five masked captors, purportedly in revenge for the mistreatment of Iraqi prisoners by U.S. military guards. The CIA said the apparent leader of the group, a man who read a written statement before drawing a large knife from his clothing, is Abu Musab Zarqawi, a Jordanian terrorist connected to the al Qaeda network of Osama bin Laden.

Before Berg evidently was captured by the terrorist group, he had spent 13 days in custody in the northern city of Mosul after being arrested by Iraqi police who believed his presence there was suspicious. During his detention, Berg was questioned three times by FBI agents, U.S. officials said.

At the Justice Department news conference called to announce an initiative against child pornography, Ashcroft was asked about the FBI's involvement with Berg. He said that after interviewing him at an Iraqi police station in Mosul, FBI agents informed the U.S.-led occupation authority in Baghdad that they had "no derogatory information" about Berg that would warrant further detention.

Ashcroft said FBI and Coalition Provisional Authority officials emphasized to Berg that he was in a "dangerous environment" and urged him to accept an offer to arrange his safe passage out of Iraq. He said Berg refused that offer, as well as government offers to advise his family and friends of his status.

"We did not develop any interest in Mr. Berg or determine in any way that he had any relationship to any activities of terror," Ashcroft said.

Ashcroft was also asked about FBI questioning of Berg in 2002 after a computer password he had used in college turned up in the possession of Zacarias Moussaoui, an al Qaeda adherent who is currently awaiting trial in the United States on conspiracy charges related to the Sept. 11, 2001, terrorist attacks. Berg's family and U.S. officials said Berg had loaned his computer and e-mail address to a man he met while riding a bus to classes at the University of Oklahoma in 1999 and that the man turned out to be a terrorism suspect who was acquainted with Moussaoui.

"The suggestion that Mr. Berg was in some way involved in terrorist activity or may have been linked . . . is a suggestion that we do not have any ability to support and we do not believe is a valid one," Ashcroft said.

He discounted the significance of Berg's reported sharing of his e-mail address and the subsequent link to Moussaoui.

"We do not believe that reflects any association with terrorist objectives or activities," Ashcroft said. "It's not uncommon for individuals from time to time to allow computer use by other individuals in university settings."

Ashcroft said he did not know whether Berg ever knew Moussaoui, adding, "I do know that the matter was resolved, and it was resolved in a way that indicated that there was no inappropriate involvement in terror."

At the White House, presidential spokesman Scott McClellan today brushed aside a reported charge by Berg's father, Michael Berg, that the Bush administration bore some responsibility for his son's death.

"My son died for the sins of George Bush and Donald Rumsfeld," Michael Berg said Thursday in an interview with radio station KYW-AM.

"This is a very difficult period for the Berg family," McClellan said. "This is a time to keep Nicholas Berg's family in our thoughts and prayers. And that's what we intend to do."

The family has asserted that Nicholas Berg was held by the U.S. military in Mosul and that his nearly two-week detention caused him to miss a flight he had booked to return to the United States on March 30.

The State Department has said that a consular official mistakenly informed the Berg family that their son was in U.S. military custody when he was actually being held by Iraqi police. But the family insists that Nicholas Berg himself informed them after he was released that he had been in military custody.