Belco was one of 339 companies fined in fiscal year 2011 and one of thousands audited that year.

Employers are required to have their workers fill out an I-9 form that declares them authorized to work in the country. Currently, an employer needs only to verify that identifying documents look real.

The audits, part of a $138 million worksite enforcement effort, rely on ICE officers scouring over payroll records to find names that don't match Social Security numbers and other identification databases.

The audits "don't make any sense before a legalization program," said Daniel Costa, an immigration policy analyst at the Economic Policy Institute, a Washington, D.C., think tank. "You're leaving the whole thing up to an employer's eyesight and subjective judgment, that's the failure of the law. There's no verification at all. Then you have is the government making a subjective judgment about subjective judgment."

An AP review of audits that resulted in fines in fiscal year 2011 shows that the federal government is fining industries across the country reliant on manual labor and that historically have hired immigrants. The data provides a glimpse into the results of a process affecting thousands of companies and thousands of workers nationwide.

Over the years, ICE has switched back-and-forth between making names of the companies fined public or not. Lately, ICE has emphasized its criminal investigations of managers, such as a Dunkin' Donuts manager in Maine sentenced to home arrest for knowingly hiring illegal immigrants or a manager of an Illinois hiring firm who got 18 months in prison.

Many employers also wonder how ICE picks the companies it probes.

"Geography is not a factor. The size of the company is not a factor. And the industry it's in is not a factor. We can audit any company anywhere of any size," Bench said. He added ICE auditors follow leads from the public, other employers, employees and do perform some random audits.

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