Federals agents raided and detained about 300 people they believe to be illegal aliens working at House of Raeford's Columbia Farms poultry plant in Greenville -- an operation that one immigration official today called the biggest workplace raid ever in the Carolinas. All told, 450 officers were involved in the raid, though not all actually entered the building. In recent weeks, seven supervisors at the plant have pleaded guilty to falsifying employment documents. A human resources manager faces 20 counts of felony immigration fraud.