The Lake County sheriff's department has participated in the raids. Most of the detainees live in Waukegan. Mexico's Chicago consulate says they include at least 25 Mexican nationals. It says some are legal permanent residents of the United States. Authorities took some detainees to Dodge County, Wisconsin.
Waukegan Mayor Richard Hyde says his city's immigrants, even the undocumented, have no reason to fear.
HYDE: If an illegal immigrant obeys the law, he has no problem. The only time that he's got a problem is when he starts breaking the law, and he gets caught and it's a felony, then you have a problem.
Immigration and Customs Enforcement says the detainees posed threats to public safety. The agency says it won't provide details until the operation ends.
I'm Chip Mitchell, Chicago Public Radio.