The FBI effort, authorized by the antiterrorism law enacted after the Sept. 11 attacks, is the first broad government check of library records since the 1970s when prosecutors reined in the practice for fear of abuses.
A Justice Department official in the civil rights division and FBI officials declined to comment Monday, except to note that such searches are now legal under the Patriot Act that President Bush signed last October.
Libraries across the nation were reluctant to discuss their dealings with the FBI. The same law that makes the searches legal also makes it a criminal offense for librarians to reveal the details or extent.
"Patron information is sacrosanct here. It's nobody's business what you read," said Kari Hanson, director of the Bridgeview Public Library in suburban Chicago.
Hanson said an FBI agent came seeking information about a person, but her library had no record of the person. Federal prosecutors allege Global Relief Foundation, an Islamic charity based in the Chicago suburb, has ties to Osama bin Laden's terror network.
The University of Illinois conducted a survey of 1,020 public libraries in January and February and found that 85 libraries had been asked by federal or local law enforcement officers for information about patrons related to Sept. 11, said Ed Lakner, assistant director of research at the school's Library Research Center.
The libraries that reported FBI contacts were nearly all in large urban areas.
In Florida, Broward County library director Sam Morrison said the FBI had recently contacted his office. He declined to elaborate on the request or how many branch libraries were involved.
"We've heard from them and that's all I can tell you," Morrison said. He said the FBI specifically instructed him not to reveal any information about the request.
The library system has been contacted before. A week after the Sept. 11 attacks, the FBI subpoenaed Morrison to provide information on the possible use of computer terminals by some of the suspected hijackers in the Hollywood, Fla., area.
In October, investigators revisited the county's main library in Fort Lauderdale and also checked a regional library in Coral Springs.
At least 15 of the 19 hijackers had Florida connections.
The process by which the FBI gains access to library records is quick and mostly secret under the Patriot Act.
First, the FBI must obtain a search warrant from a court that meets in secret to hear the agency's case. The FBI must show it has reason to suspect that a person is involved with a terrorist or a terrorist plot -- far less difficult than meeting the tougher legal standards of probable cause, required for traditional search warrants or reasonable doubt, required for convictions.
With the warrant, FBI investigators can visit a library and gain immediate access to the records.
Judith Krug, the American Library Association's director for intellectual freedom, said the FBI was treading on the rights it is supposed to be upholding.
"It's unfortunate because these records and this information can be had with so little reason or explanation," Krug said. "It's super secret and anyone who wants to talk about what the FBI did at their library faces prosecution. That has nothing to do with patriotism."
Krug tells worried librarians who call that they should keep only the records they need and should discard records that would reveal which patron checked out a book and for how long.
She is frustrated by the hate mail she says she receives when she speaks out against the Patriot Act.
"People are scared and they think that by giving up their rights, especially their right to privacy, they will be safe," Krug said. "But it wasn't the right to privacy that let terrorists into our nation. It had nothing to do with libraries or library records."
Some libraries said they will still resist government efforts to obtain records.
Pat McCandless, assistant director for public services for Ohio State University's libraries, said, "State law and professional ethics say we do not convey patron information and that is still our stance."
"To the best of our ability, we would try to support patron confidentiality," she said.