US officials have pledged to continue a crackdown on illegal immigration a day after agents arrested 1,200 people at meat-packing plants in six states.
Workers' families confronted police outside one of the plants
Homeland Security Secretary Michael Chertoff said the arrests had uncovered flagrant violations of immigration and privacy laws.
Most of the workers arrested at the Swift & Co meat-packing plants are from Central American and African countries.
Swift & Co said it did not knowingly hire illegal immigrants.
The arrests followed a 10-month investigation into alleged illegal immigrants suspected of using forged or stolen identity papers.
"Violations of our immigration laws and privacy rights often go hand in hand," Mr Chertoff said.
He said an investigation into the sale of identity papers to illegal immigrants was continuing.
Immigration and customs official Julie Myers said illegal immigration was making identity theft the fastest-growing crime in the US, Reuters news agency said.
There are an estimated 12 million illegal immigrants in the US.