Space constraints and court orders have led ICE to release migrants on monitoring programs after they’re arrested.

The number of arrests there was uncertain. Illinois officials, including the governor, said they had not been given advance notice.

No longer just campaign trail rhetoric, President Donald Trump’s insistence that immigration to the United States amounts to an “invasion” may be critical to unlocking extraordinary powers as the administration carries out his deportation agenda.

Immigration and Customs Enforcement has space to detain about 41,000 people a day, but Trump’s "border czar," Tom Homan, wants space to hold over double that amount.

Specifics of detainments have been scarce, leaving it unclear whether the criminals being targeted make up a significant share of those being captured.