While both the detainees and their lawyers say they are baffled by the detentions, some of those familiar with the cases said they believed the impetus was the interest of law enforcement officials in companies that offer young Israelis -- and perhaps others in the Middle East -- help in coming to, and working in, the United States.

''It's hard to understand,'' said Suzanne Brown, a St. Louis lawyer representing 5 of the 10 Israelis detained there. ''Just today, I talked with the I.N.S. officer in charge of the St. Louis office, who said he doesn't know who is conducting the investigation of the Israelis. And what are they investigating? I don't know.''

In Ohio, on Oct. 31, the immigration service detained nine men and two women, all of whom had valid passports and tourist visas. Nine of the 11 were released on bond on Friday, but two remain in the Medina County jail, outside of Cleveland. The next hearing for the Israelis -- all in their early 20's and recently finished with their Israeli army service -- is scheduled for Nov. 27, in Cleveland.

''It doesn't make sense that they held any of these kids as long as they did, and we don't know of any reason why they're still holding two,'' said David Leopold, the Cleveland lawyer representing them. ''You hear there's more than 1,000 detainees, and if these cases are any example, you have to wonder if they're just locking people up to make it look like they're getting somewhere on their investigation.''

Dan Nelson, a spokesman for the Justice Department, said that he was unaware of the Israeli detainees, but that generally, since Sept. 11, there has been greater scrutiny of those who violate immigration laws.