Mercedes-Benz banned a construction subcontractor from its plant in Vance, Alabama, after an CBS News investigation found that foreign workers had obtained visas on the basis of roles substantially different from those they ended up occupying.

Former workers confirmed to CBS News that the practice had been apparent since 2013, and a CBS News investigation has found that it continues to this day. The CBS News team spent four months tracking more than 200 Eastern Europeans building U.S. auto factories, traveling to Croatia to meet one former worker who spent time working in construction at an automaker's plant in the U.S. The full report aired on July 31 on both the CBS Television Network and CBSN during the premiere of "CBSN: On Assignment."

CBS News collected hundreds of videos and photos they posted on social media proudly showing off their American jobs, their work IDs, the money they were making, and the B1/B2 visas that got many of them into the United States. The visa costs less than $200 and allows foreigners to come and go for ten years. Visa holders are not allowed to work construction unless they are supervising a project which is not what appeared to be happening.

Our investigation led us us to an apartment complex in Spartanburg, South Carolina, where it appeared workers from Slovenia and Croatia were being housed by their employer nearby BMW's largest manufacturing plant in the world, built with the help of more than $250 million in tax incentives and subsidies afforded to BMW since 1992.

At Mercedes in Alabama, we found dozens of Eastern European workers, and some Americans, entering the construction project just before dawn.

This is how the Eastern Europeans usually end up working in the United States:

When a carmaker like Mercedes wants to expand its plant, they hire a contractor, like the German corporation, Eisenmann, to build parts of it. Eisenmann then subcontracts smaller companies to build parts of the plant and some of those companies hire labor from Eastern Europe.

After a chain of communication with CBS News, Mercedes Benz confirmed that they had asked its subcontractors for written evidence that they were in compliance with visa law, and had banned one of the subcontractors from their plant.

In a statement issued by the German carmaker, they said:

"When MBUSI was first notified of the CBS B1/B2 visa abuse allegations, MBUSI required written confirmation from the relevant contractors and their subcontractors that all of their employees are legally authorized to work in the U.S. "When MBUSI first received an allegation of wrongdoing by a specific subcontractor, that subcontractor was immediately banned from MBUSI's site. Only when the contractor proves to MBUSI's satisfaction that all of its subcontractor's employees are legally authorized to work in the U.S. will they be allowed back on site."

The full statement is featured below. Mercedes-Benz was not the only automaker identified as having employed European workers to build their plants. The CBS investigation also found European workers at Volvo and BMW in their respective plants at Charleston and Spartanburg, South Carolina. BMW and Volvo also responded to requests for comment from CBS News, saying that the visa requirements for the foreign workers were the legal responsibility of the subcontractors who employed them and that the auto companies require that all contractors and subcontractors adhere to all employment, immigration and safety laws. Those statements are located here.

Full statement from Mercedes-Benz:

Since we emailed last time we wanted to let you know what further actions we have taken as part of our ongoing effort to enforce compliance by onsite contractors with all applicable rules and regulations.

· Compliance with all applicable laws is of utmost importance to MBUSI.

· MBUSI contractually requires all of its contractors to comply with all applicable laws, including those laws and regulations related to immigration, safety, wages and hours.

· MBUSI's Vance, Alabama plant is one of the safest automotive plants in the United States.

· We conduct daily meetings with our contractors concerning safety, and perform daily audits throughout the plant where construction is ongoing to make sure that safe practices are being observed.

· When MBUSI was first notified of the CBS B1/B2 visa abuse allegations, MBUSI required written confirmation from the relevant contractors and their subcontractors that all of their employees are legally authorized to work in the U.S.

· When MBUSI first received an allegation of wrongdoing by a specific subcontractor, that subcontractor was immediately banned from MBUSI's site. Only when the contractor proves to MBUSI's satisfaction that all of its subcontractor's employees are legally authorized to work in the U.S. will they be allowed back on site.

· Additionally, MBUSI has begun an audit of its contractor/subcontractor employees to verify our contractors' and subcontractors' confirmations that their employees are legally authorized to work in the U.S. and are paid in accordance with U.S. law.

· MBUSI absolutely condemns all abuse of any immigration, safety, and wage and hour regulations, and we welcome any specific information you may have concerning any alleged violations of these laws. MBUSI will immediately investigate any such allegations and take prompt and appropriate action.