"Employers and workers alike should be on notice that the status quo has changed," Chertoff said in a statement. "These enforcement actions demonstrate that this department has no patience for employers who tolerate or perpetuate a shadow economy."

The internal enforcement plan announced Thursday is the second phase of the Secure Border Initiative, a multi-year plan to secure the nation's borders and reduce illegal migration. The first phase remains focused on securing the borders.

Its goals include identifying and removing criminal aliens, immigration fugitives and other immigration violators, along with building strong worksite enforcement and compliance programs. It's also targeting criminal infrastructures at home and abroad that support illegal immigration, such as immigrant smuggling organizations and document and benefit fraud organizations.

The House passed legislation last year aimed at getting tough on employers who hire illegal workers and that would require employers to use a national system to electronically verify workers' legal status.

The Senate is expected to resume debate next week on legislation that would include guest worker status for undocumented workers who meet certain requirements.

Community activist Tony Yapias of Proyecto Latino de Utah said he'd received concerned calls about the crackdown all day Thursday.

"We feel that the timing is very unfortunate because national efforts are under way to work together on creating a compromise that may include a guest worker program that would allow people arrested today to come into compliance and work legally in the United States," Yapias said.

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Contributing: Associated Press

E-mail: dbulkeley@desnews.com