One of the newly discovered FBI documents handed over to Timothy McVeigh's lawyers calls into question evidence used to discredit a witness who testified he saw McVeigh with a second man an hour before the bombing, according to a published report.

The witness' credibility came under attack in part because a prosecutor said the man did not come forward for six months after the Oklahoma City bombing. But the FBI document, known as a lead sheet, confirmed he came forward two days after the bombing, The New York Times reported Sunday, citing an unidentified source familiar with the case.

In all, 4,034 pages of materials about the April 1995 bombing of the Alfred P. Murrah Federal Building have been found that should have been turned over to McVeigh's attorneys years ago. The FBI says computer and record-keeping blunders caused the problem and that some documents were not material to the case.

McVeigh's execution was delayed this month until June 11 after Justice Department officials acknowledged the existence of the documents.

The lead sheet pertained to Morris John Kuper Jr., a witness who told the FBI he saw a man resembling McVeigh walking with another man along the sidewalk near the federal building an hour before the bombing.

In the trial of McVeigh's co-defendant, Terry Nichols, prosecutor Patrick Ryan challenged Kuper's credibility by saying he had made no attempt to contact the FBI before Oct. 24, 1995.

"I certainly would never intentionally tell the jury someone had not come forward for six months if I knew they had come forward a couple of days after the bombing," Ryan, now a lawyer in private practice, told the Times.

But prosecutors also questioned discrepancies between Kuper's statements to the FBI and his testimony at trial. Kuper was one of many witnesses called by Nichols' defense attorneys to attempt to show someone other than Nichols, a "John Doe No. 2," helped McVeigh plan the bombing.

On Friday, Chris Watney, a spokeswoman for the Justice Department, told the Times she could not comment on the details of the documents.

"We have reviewed all of the documents carefully and remain confident that nothing in them undermines Mr. McVeigh's admission or the justice of his sentence," she said.

Nathan Chambers, a member of McVeigh's legal team, said Saturday he could not comment on any of the FBI documents. He said attorneys had not yet decided whether to seek a new trial or a stay of execution.

Sketches of a John Doe No. 2 circulated after the bombing, but federal officials eventually identified him as an Army private who had no role in the attack. McVeigh has emphatically denied the existence of a John Doe No. 2. Lawyers for Nichols have asked the U.S. Supreme Court to reconsider his appeal, citing the newly released FBI documents.