An FBI agent at the center of a foul-up over Oklahoma City bombing documents told lawmakers that he waited for months to alert his superiors because he wanted to ascertain the magnitude of the problem, according to a memo on his meeting with lawmakers. 

Danny Defenbaugh, the lead investigator of the Oklahoma City bombing case who was in charge of collecting investigative documents, said the FBI had an inkling that something was amiss as early as January, said the summary of a briefing Defenbaugh gave to members of the Senate Judiciary Committee. The summary was obtained by The Associated Press on Thursday. 

Why the FBI disclosed just a week before Timothy McVeigh's scheduled execution that it had failed to turn over more than 3,000 investigative records has been one of the most perplexing questions in the documents controversy. 

FBI field offices were asked in late December to send all investigative materials to Oklahoma City to be archived. Defenbaugh told lawmakers that archivists discovered a single document that had not been turned over to McVeigh's lawyers as required, according to the summary. 

By early February, more items began to arrive that had not been turned over. Over the next several weeks, many other items were discovered. 

McVeigh's execution, originally set for May 16, was delayed by the Justice Department until June 11 after the FBI revealed that investigative records had not been turned over to McVeigh's lawyers. 

McVeigh's attorneys are examining the documents to determine whether they provide an opportunity to challenge McVeigh's conviction and death sentence for the 1995 blast that killed 168 people and injured hundreds of others. 

Asked why he waited until May to notify FBI higher-ups, Defenbaugh said he wanted to be completely sure what the problem was and how bad it was, the summary says. 

Defenbaugh seemed to take offense at the question, according to a source familiar with the conversation. "He was affronted," said the source, who spoke on condition of anonymity. 

Citing the unreliability of the FBI's main computer system, Defenbaugh said he opted in 1995 to enter all the bombing documents into a separate database in Oklahoma. As it turns out, 254 of the items never turned over to McVeigh's attorneys actually had been entered in the FBI's computer system. 

According to the memo, Defenbaugh told lawmakers that in hindsight he should have checked the FBI computer system for any documents.