(page 2 of 10) The operation is being conducted under great secrecy, with defense attorneys at times forbidden to remove documents from court and a federal gag order preventing officials from discussing the detainees. Law enforcement officials have refused to identify lawyers representing people who have been detained or to describe the most basic features of the operation. The officials say they are prohibited from disclosing more information because of privacy laws, judges' orders and the secrecy rules surrounding the grand jury investigation of the Sept. 11 attacks. The result has been confusion over exactly who is being counted in the government's official tally of 1,147 detainees and who is still being held. When asked directly how many people have been released, Justice Department officials say they are not keeping track. Of the 1,147, Justice officials have specifically singled out only 185 detainees who are being held on immigration charges. An INS official described them as "active cases" believed to have "relevance to the investigation." To try to illuminate this hidden campaign, The Washington Post identified 235 detainees and examined the circumstances of their cases. The analysis of these cases -- located through court records, news accounts, lawyers, relatives and friends -- shows that three-fifths of the detainees found by The Post are, like Mubeen, being held on immigration charges. Seventy-five have been released. A small, as-yet-unknown number are being held on "material witness" warrants, an indication that investigators believe they have information vital to the probe. Another small number -- perhaps 10 -- are believed to lie at the center of the investigation, with ties to the al Qaeda network or some knowledge of the hijackers. But sources say none of those men is cooperating. The 235 identifiable cases reveal the essential nature of the current effort: It appears to be less an investigative search for accomplices to the Sept. 11 attacks than a large-scale preventive operation aimed at disrupting future terrorism. That is evident, in part, from the fact that none of the detainees has been charged in the plot or with other acts of terrorism. In addition, the pace of detentions has accelerated visibly as government officials have received information about new threats and issued public warnings -- spiking sharply, for example, after rumors of planned attacks Sept. 22.         PREVIOUS PAGE RETURN TO BIO NEXT PAGE