A South Carolina unit of House of Raeford Farms has been charged as part of an ongoing federal investigation into immigration violations.

A federal grand jury on Tuesday indicted Columbia Farms, a subsidiary of the Raeford-based poultry company. The move shows a progression by federal prosecutors as they investigate workers, managers and now the company itself.

The ongoing investigation has already resulted in charges against the complex manager of the company's Greenville, S.C., plant, its human resource manager, about a dozen supervisors and more than 300 workers. A filing this week in U.S. District Court in Greenville added Columbia Farms to what's called a "second superseding indictment" that included the two managers.

Federal authorities allege Columbia Farms hired illegal workers from around 2000 until October 2008, when U.S. Immigration and Customs Enforcement agents raided the plant.

House of Raeford is one of the nation's top chicken and turkey producers with operations in the Carolinas and Louisiana.

In a February 2008 series on workplace safety in the poultry industry, the Charlotte Observer reported that some company managers knowingly employed illegal immigrants. Current and former supervisors told the paper the plants prefer undocumented workers because they're less likely to question working conditions for fear of losing their jobs or being deported.

To read the complete article, visit www.charlotteobserver.com.