Two dozen Illinois employers connected to public-safety infrastructure face a federal audit of their hiring records. Immigration officials say they have reason to believe the companies are hiring illegal immigrants.

The 24 Illinois employers are among 1,000 nationwide that authorities say they’ve notified for auditing. Immigration and Customs Enforcement Assistant Secretary John Morton spoke about the effort this afternoon.

MORTON: We selected these businesses as a result of investigative leads and intelligence and because they have a connection to public safety and national security -- for example, power plants, food industry, government facilities and the like.

Authorities aren’t identifying the employers. The audits include a review of I-9 forms, which companies are required to complete for each hire. The audits can lead to civil penalties and criminal prosecution.

They’re part of a shift in workplace immigration enforcement toward employers and away from raids targeting workers. Department of Homeland Security Secretary Janet Napolitano announced that shift in April.

The Pew Hispanic Center estimates that 450,000 unauthorized immigrants live in Illinois.

Update: Immigrant Advocates Slam Federal Audits.