The mystery of how confidential debate preparation materials made their way from Texas Gov. George W. Bush's inner circle to Vice President Gore's debate coach is not going to be officially solved anytime soon.

After an initial round of interviews and evidence-gathering by the FBI, the investigation in recent weeks has been much less visible. Members of the Gore and Bush camps said they are frustrated but resigned to the lack of resolution before the public goes to the polls.

Attorney General Janet Reno, asked last week whether the investigation has been routed onto a slow track until the election is over, declined to comment. She said only that it is still pending and all appropriate steps are being taken.

Law enforcement officials said the only way the debate tape probe would have been completed before the presidential election would be if someone confessed. Moving forward with anything less would disrupt the election, they said.

The focus of the investigation has been on Bush's Austin media firm, Maverick Media, and a Maverick employee who was captured on post office surveillance tape Sept. 11 mailing an Express Mail package. An Express Mail package containing briefing materials and a videotape of Bush practicing for his televised debates against Gore was mailed at precisely that time from the same Austin post office. It was delivered two days later to Gore's then-debate coach, former congressman Thomas Downey, who contacted the FBI when he realized the package contained materials leaked from the Bush operation.

"My suspicion is we're not going to find out anything for months," said Rusty Hardin, a lawyer representing Maverick Media owner Mark McKinnon. He said he has had several conversations with Justice Department prosecutors about the case. "Investigators are still talking to witnesses," he said. "I think they are waiting to schedule grand jury appearances until after the election." Hardin and other lawyers involved in the case agreed it would be improper for investigators to move just before an election. "Any responsible public integrity prosecutor would do it the way they are doing it," Hardin said.

FBI Director Louis J. Freeh assured the Bush campaign that the incident would be fully investigated. The Justice Department, meanwhile, has been weighing whether the alleged action involved a federal crime such as mail fraud or theft, and as a preliminary matter has decided the actions constitute possible criminal acts.

The Maverick Media employee taped at the Austin post office, Juanita Yvette Lozano, is on paid leave until the investigation is over, according to Hardin. Neither Lozano nor her lawyer were available to discuss the investigation, but she has maintained her innocence since the beginning.

An official in the Bush camp said the campaign has been informed that an FBI analysis of hair found on the tape was not a DNA match with Lozano.

One of the mysteries is whether a campaign briefing book that belonged to McKinnon was the one copied. Stuart Stevens, a Bush media consultant who works with McKinnon, said that in September, McKinnon's debate briefing book was found on the street outside Bush campaign headquarters by a passerby who returned it. Stevens said McKinnon put the book down on the sidewalk to help Stevens load some equipment into his car. The two then drove off to Bush's ranch, inadvertently leaving the book behind. The debate practice tape was made at the ranch the following day, he said.

Stevens said the campaign and Maverick Media officials continue to believe in Lozano's innocence, despite the post office evidence. He said various media consultants, some of them Democrats, used the editing facility in the building with Maverick Media. One of them could have copied the tape and briefing book, he speculated, then put it in an outgoing mailbox, which Lozano then unknowingly took to the post office with other items.

Some campaign officials are frustrated the FBI has not interviewed people with Democratic ties who had access to the building where Maverick Media is located.

Meanwhile, the Dallas Morning News reported new details last week in the 1986 incident in which Bush's chief campaign strategist, Karl Rove, was suspected of bugging his own office and blaming a rival campaign. The Dallas paper, citing documents released under the state's open records law, said the FBI suspected the firm Rove hired to sweep his office might have surreptitiously planted the bug to impress its employer.

Staff writers David Vise and Lois Romano contributed to this report.