( CNN ) -- Federal immigration agents arrested about 300 workers Tuesday in a raid at a poultry processing plant in Greenville , South Carolina , the Department of Justice said . The agents executed a criminal search warrant at 9 a.m. at the Columbia Farms poultry processing plant , capping a 10-month investigation into the plant 's employment practices , said Barbara Gonzalez , a spokeswoman for Immigration and Customs Enforcement . About 58 of those arrested were allowed to return to their homes to take care of their children or for other humanitarian reasons , she said . The others were to be held in an ICE detention facility in the area . `` They are all illegals , '' Gonzalez said . `` We have charged them with being in violation of U.S. immigration laws . '' The investigation has already resulted in criminal charges being filed against 11 supervisors and a human resources manager , she said . Maria Juan , 22 , was one of about 50 relatives and friends of workers who huddled at the edge of the plant after the raid , some weeping and others talking frantically on cell phones , The Associated Press reported . She was seeking information about her 68-year-old grandmother , a legal immigrant from Guatemala who went to work without identification papers but was later released , the AP reported . `` Families are going to be broken apart , '' Juan told the AP . `` There will be kids and babies left behind . Why are they doing this ? Why ? They did n't do anything . They only wanted to work . '' No one from Columbia Farms or from its parent company , House of Raeford Farms in Raeford , North Carolina , responded immediately to telephone messages . The Charlotte Observer newspaper first reported in February that plant workers were in the country illegally and company managers knew it , the AP reported . The raid `` is a drop in the bucket '' that is unlikely to persuade anyone in the United States illegally to go home , said Dan Kowalski , an Austin , Texas-based lawyer specializing in immigration law . He questioned the conclusion by Gonzalez and ICE that all of those arrested are indeed illegal immigrants . `` A judge has to say that , they ca n't just say that , '' he said .
Federal immigration agents conduct raid at plant in Greenville , South Carolina . About 58 allowed to return to their homes to take care of their children . No response from Columbia Farms or parent company , House of Raeford Farms .