Legal? You sure? I live 3 hours to the east of you and I happen to know that there are a number of immigrants who have forged paperwork to work. I'm sorry, but forged documents are such a problem, I question the status of any non citizen of Mexican origin. I moved from Arizona just over a year ago and previous to that spent my youth in south Florida so in case you think I carry some homogenous midwestern bias, thought I should point that out.
If you KNOW they have forged paperwork, could you please explain how? Did they tell you? Do you know the forger? Do you recognize forged paperwork when you see it?
If you definitely know that the paperwork is forged, I suggest you contact INS and report both the workers and the employers.
Here in Indianapolis we have had a few raids on illegals, like the company that was making racing helmets a few years ago. They are sent home, you know. Please make that call, if you know this for a fact.