(FORTUNE Small Business) -- Congress has yet to nail down any of the details on immigration reform, but federal officials are already stepping up their enforcement - with an eye on small employers.

In June special agents from the U.S. Immigration and Customs Enforcement (ICE) office in Wichita arrested 11 illegal aliens at three local scrap-metal yards and arranged to have them deported. A few months earlier, ICE officials arrested 18 illegal aliens who worked at a shipyard in San Diego. In both cases, the business owners weren't charged and said they didn't know the workers were illegal. Still, they paid an immediate price in lost productivity while they searched for replacement employees.

Tricia Smith, founder of Secure Check, in her Cincinnati office

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Given the rising public opposition to illegal immigration, enforcement actions are likely to become more aggressive.

All U.S. employers must fill out federal I-9 forms on new hires that document applicants' Social Security numbers and permits to work in the U.S., and those documents must be saved for at least three years.

Ignoring these steps or knowingly hiring an illegal worker carries a penalty as high as $10,000 and six months in prison. Even an accidental error in filling out and filing I-9 forms can cost the employer $110 to $1,100 for each affected employee.

The U.S. government knows that job applicants aren't always honest when a paycheck is at stake, so the Social Security Administration offers a joint program called the Basic Pilot. It allows employers to check prospective employees' Social Security numbers and work permits against government databases online. This screening is currently voluntary; about 11,000 companies in the U.S. participate, most of them large.

Smaller companies usually lack the time and staff to check every new hire's documentation against the federal files. Some small employers might see checking as a problem, but Tricia Smith, owner of a background-screening firm in Columbus called Secure Check (securecheckinc.com), identified it as an opportunity.

With just ten workers and 2005 revenues of $670,000, Secure Check is a small player in the $2-billion-a-year background-check industry. But Smith, 35, anticipates that her 2006 revenues will rise to $900,000, in part because she has added I-9 verification to her offerings.

Secure Check coordinates with a company called Form I-9 Compliance (formi9.com), based in Newport Beach, Calif., that provides access to Basic Pilot databases. (Employers cannot go straight to Form I-9 Compliance; instead, it sells access to several dozen screening companies around the U.S., including Secure Check, that offer the information to clients.)

Smith and her investigators store I-9 data in an electronic format using Form I-9 Compliance's proprietary web portal, which can spot errors an employer may make in filling out the forms. When the electronic I-9 is complete, Secure Check can save it for the client's records ($4 for each employee) or check its contents against the appropriate government databases ($12 for each employee, with volume discounts). Secure Check's fee includes 90-, 60-, and 30-day warnings when an employee's work permit is about to expire.

"This takes the burden of authenticating someone's right to work off the employer's shoulders," Smith says.

So far, Secure Check has only offered I-9 screening to one (decidedly large) client: Spherion Staffing of Columbus, which screens several hundred thousand interviewees each year for temporary and full-time positions in Ohio and Kentucky. After other vendors' background checks cleared job applicants, Secure Check revealed "extensive rap sheets," says Spherion group vice president Dan Dolan. As a result, he says, he trusts Secure Check to deliver reliable reports on prospective employees' I-9 status too.

Although Smith will do I-9 entry and screening on an à la carte basis, she expects most of her customers will want to bundle it with other services, such as criminal screening, drug testing, or reference checks.

"There's no such thing as a one-size-fits-all background check," she says.

Is checking immigration status beyond what a small company should be expected to do? Have immigration laws affected the way your company functions? Tell us what you think.

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