Six days before Timothy McVeigh was scheduled to be executed for the Oklahoma City bombing, the Justice Department yesterday gave his attorneys thousands of pages of FBI documents that officials said were mistakenly withheld before McVeigh's 1997 trial.

The development caught McVeigh's attorneys by surprise, and was the first potential obstacle in what has been a steady march toward Wednesday's execution since McVeigh abandoned his appeals in December and announced he was prepared to die.

Attorney Nathan Chambers said he had spoken to McVeigh after the documents were delivered to his office in Denver. McVeigh's lawyers declined to say whether he would request a stay of the execution.

"Mr. McVeigh is going to think about it and decide how he wants to proceed," Chambers told the Associated Press. Chambers and Rob Nigh, McVeigh's other attorney, did not respond to repeated calls seeking comment.

Justice Department officials said the documents were missed in previous searches of computerized files in FBI field offices around the country, and located only recently during a routine archiving of records. Officials described the error as inadvertent.

Justice Department attorney Sean Connelly said in a letter to McVeigh's lawyers that "we do not believe anything being produced [bears] on the federal convictions or sentences of Timothy McVeigh" or co-conspirator Terry Nichols. "Similarly, we do not believe anything in the materials makes even a prima facie showing of either man's actual innocence."

A copy of Connelly's letter was sent to U.S. District Judge Richard Matsch, who presided over the separate trials of McVeigh and Nichols. If McVeigh seeks a stay of execution, his attorneys would have to file the motion with the 10th Circuit Court of Appeals.

Richard Burr, a Houston lawyer who specializes in death penalty cases and was a member of the defense team at McVeigh's sentencing, said the execution should be delayed, regardless of whether McVeigh wants to die.

"What ought to happen is, the government itself ought to withdraw the execution date immediately," Burr said. "The attorney general should announce immediately that he is withdrawing the execution date to make sure that no opportunity that might be available to Timothy McVeigh is left ungiven because the FBI made a mistake."

James S. Liebman, a Columbia University law professor who helped conduct a nine-year study of death penalty appeals across the country, said the new development is "something I've just never heard of. . . . I can tell you, it's extremely rare if it's ever happened before."

Survivors of the blast and family members of the victims were stricken. "I feel sorry. I feel nauseated," said Marcia Kight, who lost her 23-year-old daughter in the bombing. "It's been an emotional roller coaster for six years. But if it has to be examined, it has to be. The last thing we want is to make a martyr out of this guy."

McVeigh is scheduled to die by injection at the federal penitentiary in Terre Haute, Ind., for detonating a massive truck bomb in front of the Alfred P. Murrah Federal Building, killing 168 people, including 19 children. Thousands of journalists, protesters and onlookers are expected to converge there beginning early next week.

In a new book, McVeigh admitted culpability for the first time, several months after he gave up his legal appeals. He also let pass the deadline for requesting executive clemency from President Bush.

The missing documents were discovered during a routine "archival search" for records connected to the McVeigh case, the Justice Department said. According to Connelly's letter, the documents come from 46 FBI field offices outside Oklahoma City.

About 3,100 pages of witness interviews, reports and correspondence, plus photographs and tapes, were turned over to McVeigh's lawyers, sources said. Two government sources said some material may duplicate information previously disclosed to the defense. But another federal source close to the case said most of the material had not been seen by the defense.

Sources said a number of the "302 forms," which are official reports of interviews conducted by FBI agents around the country, pertain to "John Doe No. 2" -- a suspect who was described by witnesses soon after the blast but who never materialized.

Connelly's letter said FBI Director Louis J. Freeh and the agent in charge of the bombing probe "had requested on numerous occasions" that field offices turn over materials related to the case and "had received assurances that all such materials had been forwarded."

Justice Department spokeswoman Mindy Tucker said while the documents would not have changed the case's outcome, "the Department is concerned that McVeigh's attorneys were not able to review them at the appropriate time."

FBI officials blame the lapse on the bureau's outdated computer records system, which they said did not locate the documents during previous searches. The latest call for documents required agents in FBI field offices to search their files manually, officials said.

Officials said the FBI conducted nearly 20,000 interviews during the bombing investigation.

The FBI is in the midst of building a new computer system. It had previous problems disclosing key records.

One recent lapse came during the investigation of former Los Alamos nuclear lab scientist Wen Ho Lee. U.S. Sen. Arlen Specter (R-Pa.) complained in 1999 that the bureau found "a great many documents" relating to the case that should have been turned over much earlier.

In the McVeigh case, "there's nothing intentional here," one official said. "But should they have been located in the first go-around? Absolutely. . . . This just demonstrates the inadequacy of the bureau's computerized record system."

In his study, published last summer, Liebman and other researchers reviewed the appeals of 5,760 inmates sentenced to death by state courts between 1973 and 1995, and found that two-thirds of the appeals resulted in new trials. In a significant percentage of overturned convictions, Liebman said, the main problem was the failure of law enforcement authorities to turn over important documents to defense lawyers before trials.

But McVeigh's situation is different, Liebman said. In many cases in the study, defense attorneys and prosecutors spent years "fighting and arguing [in appellate courts] over access to documents, with the defendant claiming that the state had material and exculpatory information that it was refusing to turn over."

Liebman said he did not believe "there's an established standard" for granting of a stay of execution in circumstances such as these. "It's something that would have to be up to the discretion of the judge," he said.

For many survivors and relatives of the victims -- 300 of whom are expected to witness the execution on a closed-circuit feed in Oklahoma City -- all that matters is that McVeigh has admitted guilt.

"As far as I am concerned, he confessed. He said he did it," said Roy Sells, who lost his wife in the blast. "What do all these papers have to do with it?"

At the U.S. Penitentiary in Terre Haute last night, prison officials contemplated the news from Washington. "We are just all waiting to see McVeigh's people's take on all this," said Marybeth Cully, public affairs spokeswoman for the U.S. Bureau of Prisons.

Romano reported from Tulsa. Staff writers Anne Hull in Terre Haute and Paul Duggan in Austin contributed to this report.