Rather than send investigators out knocking on doors, law enforcement officials in Michigan are sending letters today to hundreds of young Middle Eastern men who have come to the United States on temporary visas in the last two years, inviting them to make appointments for interviews regarding the Sept. 11 terrorist attacks.

The decision by the antiterrorism task force in the Detroit area, which is responsible for contacting about 700 of the 5,000 visitors sought for questioning nationwide, comes after two weeks of complaints from lawyers, community groups and local police chiefs that the vast canvass order by the Department of Justice unfairly singles out people based on religion or nationality and would be too time-consuming.

"The letters represent a conscious decision by our district to initiate contact with the people who will be interviewed in the manner that will be least intrusive," said Jeffrey Collins, the United States attorney for the Eastern District of Michigan, which is home to the nation's largest concentration of Arab-Americans.

Mr. Collins refused to say what the authorities would do about those who failed to call. About a dozen of his counterparts around the country declined to comment on Detroit's approach or explain how they would carry out the interviews. Several indicated that they had yet to begin the project, though Washington has asked that all interviews be conducted by Dec. 21.

Separately, Attorney General John Ashcroft yesterday defended the widespread detention of immigrants who had been swept up in the aftermath of the attacks, saying the arrests had "made America grow stronger, not weaker," and had been instrumental in "winning the war on terrorism."

In an eight-page memorandum outlining guidelines for the interviews, the Justice Department instructed local officials to check visitors' passports and visas. They are also to be asked about their visits to local landmarks and foreign countries; about their sources of income, scientific expertise and access to weapons, including anthrax; and for a list of phone numbers of friends and relatives.

"The individual should be asked if he is aware of anybody, including himself, who has received any training which could be applicable to terrorist activities," said the memorandum, whose contents were disclosed on Saturday in The Detroit Free Press. "You should ask whether the individual is aware of any persons who have sympathy for the Sept. 11 hijackers or other terrorists."

Civil liberties advocates and Arab- American leaders said the use of letters in Detroit was a positive step toward making the interview process more dignified, but they continued to express concern about the content of the questions and the process of compiling the list. The 5,000 people being sought are men from 18 to 33 who have entered the country since Jan. 1, 2000 on tourist, student or business visas from countries linked to terrorism.

"You're asking people what are your political beliefs and what are the beliefs of your friends," said Hussein Ibish, a spokesman for the American Arab Anti-Discrimination Committee. "That is a set of questions that has a dark history in our country."

The Detroit letter emphasizes, with a boldface sentence, "We have no reason to believe that you are, in any way, associated with terrorist activities." The interviews are voluntary, it said, adding that "it is crucial that the investigation be broad based and thorough, and the interview is important to achieve that goal."

The letter, which asked that people contact the United States attorney's office by Dec. 4 and promised to accommodate their schedules in setting up interviews, said, "It is quite possible that you have information that may seem irrelevant to you, but which may help us piece together this puzzle."

Mindy Tucker, a spokeswoman for the Justice Department, said she was unaware of any other region that planned to send out letters rather than contact interviewees in person, but that the approach seemed fine.

"One of the reasons that we enlisted state and local assistance is that they will know best how to conduct these interviews," she said. "We realize that each task force in each of the districts will have a different way of going about accomplishing the task."

Even as they praised the letters, lawyers and community leaders raised doubts about the strategy's effectiveness. Many foreigners may be reluctant to come forward, they said, including those who may have violated their visa agreements and fear that they will land in jail. Others, particularly those who grew up under repressive regimes, may be intimidated by the notion of contact with the government.

"Some of them may not call," said Hassan Qazwini, Imam of the Islamic Center of America, Detroit's largest mosque. "Not because they have something to hide, but because they don't want to have the hassle of going to meet the officials and experience the panic they sometimes have experienced in their own countries."

Lucas Guttentag, director of the Immigrants' Rights Project of the American Civil Liberties Union, said the 5,000 interviews were particularly troubling because of other Justice Department initiatives, like the detention of some 500 people on immigration violations, the increased scrutiny on new visa applicants from certain countries, and the use of military tribunals for those suspected of terrorist activity.

Asked at a Washington news conference, Mr. Ashcroft promised yesterday that he would provide an updated tally later this week of how many people had been arrested and how many remained in jail. But he warned that few specifics would be forthcoming and that the government would continue to withhold their identities.

"It would be a violation of the privacy rights of individuals for me to create some kind of list of all of them that are being held," he said when asked why he had not identified those arrested.

He added, "I'm not going to develop some sort of blacklist of individuals who have been held."

Mr. Ashcroft also said that those arrested since Sept. 11 "are not being held in secret" and that all had been given an opportunity to contact lawyers.

Senators Russell D. Feingold of Wisconsin and Patrick J. Leahy of Vermont, both Democrats, said Mr. Ashcroft's response was insufficient.

"To the extent that privacy concerns exist, they are overcome by the need for public scrutiny of the actions taken by those charged with enforcing our laws," said Mr. Feingold, one of several lawmakers who have formally requested details about the detainees. "A far more significant injury to the detainees' reputations comes from treating them as a single group possibly associated with the terrorists."

Mr. Leahy said in a statement, "It's time we know who these people are and why they're being held."

Bill Berger, president of the International Association of Police Chiefs, said that the Detroit area's strategy of contacting people by mail was a good one, but that in most of the country, where fewer were wanted for questioning, local agencies would have no problem conducting the canvass.

He minimized the reservations expressed by a few of his members, like Andrew Kirkland, the acting police chief of Portland, Ore., who has said he would refuse to take part because the interviews violated the state constitution.

"The chiefs that I've talked to, I think, will do anything possible to assist this country in what we're going through right now," said Mr. Berger, who is police chief of North Miami Beach, Fla.