WASHINGTON - The vast majority of the more than 900 people the federal government acknowledges detaining after the Sept. 11 attacks have been deported, released or convicted of relatively minor crimes not directly related to terrorism, government documents show.

An undisclosed number - most likely in the dozens - are or were held as material witnesses, people the government asked a court to detain because they may have direct knowledge or connection to terrorism.

At the request of The Associated Press, the Justice Department provided its most thorough public accounting of the people arrested in the immediate aftermath of the attacks.

Only six of the 765 people arrested by the federal government on immigration violations still are held by the Immigration and Naturalization Service. The rest have been deported or are free in the United States awaiting a final decision on whether they can stay. Some will be permitted to remain in this country because they cooperated in the investigation, Justice Department officials say.

An additional 134 people were charged with criminal offenses, with 99 found guilty through pleas or trials. Many of the crimes bear no direct connection to terrorism. The Justice Department said lesser charges often are used to get a dangerous person off the streets before more serious crimes are committed.

In a statement that accompanied the documents on the arrests, the department said it "has not, and will not, hesitate to use any available charge or tool to remove dangerous individuals from the streets and protect American lives."

The effort has drawn criticism from public interest groups, which are battling the government in court to obtain disclosure of the names and circumstances of those arrested - many of whom spent weeks or months in custody for relatively minor offenses.

Critics are concerned that such mass arrests, even in time of war, could be a prelude to more serious threats against civil liberties and constitutional rights.

"I believe the administration has already overstepped its bounds, and we should take it to task for that now," said Geoffrey Stone, law professor at the University of Chicago. "We as a nation do not want to wait to raise the cry until after the government has moved to more extreme measures."

Justice officials say the detentions and legal processes were fair and met constitutional obligations.

"As in other criminal investigations, we seek to bring to justice those responsible for the attacks," said department spokeswoman Barbara Comstock on Wednesday. "This investigation, however, has another important purpose as well - to protect Americans from additional acts of terror."

Many of the criminal charges involved visa or passport forgery, perjury, identification fraud and illegal possession of weapons. But they also include the counts brought against Zacarias Moussaoui, the only person charged in connection with the Sept. 11 hijackings, and those against attempted shoe-bomber Richard Reid.

The most common immigration violations were overstaying a visa, illegal entry or entering the country by fraud.

Steven Shapiro, national legal director for the American Civil Liberties Union, said it is clear that dozens of people with no connection to terrorism "just got caught up in this dragnet."

He said the sweep was comparable, on a lesser scale, to previous U.S. actions such as internment of Japanese-Americans during World War II and blacklists of suspected communists during the Cold War.

"This country has repeatedly overreacted in the face of threats and perceived threats," Shapiro said. "We have always looked back later and regretted what we did."

Counting local and state detentions, about 1,200 people were rounded up in the terrorism investigation shortly after the attacks. The numbers released by the Justice Department do not include those local cases or more recent ones, such as the arrests of six men alleged to be members of an al-Qaida cell based near Buffalo, N.Y.

The Justice documents do not say how many of the 281 people released so far had nothing to do with or no knowledge of the terror attacks. Many of these people could still be deported, pending the outcome of their immigration cases, but were released because they were determined to pose no threat to the United States.

In some cases, the government decided to simply deport someone it could have prosecuted for a crime, according to Justice officials. The documents say prosecutions were avoided in some cases to prevent disclosure of sensitive intelligence sources and methods or classified evidence.

The rest of the detainees are or were being held as material witnesses, which critics contend can be a way to keep someone in custody indefinitely without charge.

Justice officials defend the practice, saying a judge must approve whether a person can be held as a material witness - and only then if the person has information relevant to an investigation and might be a flight risk.

Justice officials refuse to disclose even the total number of material witnesses, citing prohibitions against releasing the ongoings of secret grand jury investigations.

The government continues to resist releasing the names of any detainees, which 22 public interest groups are seeking through lawsuits in federal court. Officials say al-Qaida and other groups could find out how the United States tracks down terrorists or learn other secrets if the names were made public.

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