Immigration officials raided 40 locations of Houston-based pallet-making company IFCO in 26 states on Wednesday, arresting six former and current IFCO mangers who were charged with knowingly hiring undocumented workers. They could face up to 10 years in prison if found guilty.
Homeland Security Secretary Michael Chertoff, who now oversees immigration enforcement, told reporters that the surprise raids against IFCO had occurred on Wednesday.
"Employers and workers alike should be on notice that the status quo has changed," Mr Chertoff said. "This department has no patience for employers who tolerate or perpetuate a shadow economy," he said.
The company hired a government informant, and then sent him to recruit other undocumented workers and obtain for them falsified work documents, according to officials.
Of IFCO's 5,800 workers, more than half carried invalid work papers, immigration officials said.
An estimated 12 million undocumented foreigners live in the United States, and recent bids by Congress to define a policy triggered widespread protests by pro-immigrant and Hispanic groups.
Congressmen can't agree
Millions of undocumented workers marched earlier this month in US cities nationwide to pressure Congress for favorable reforms.
However, Congress could not agree on a path to follow. President George W. Bush promoted a guest-worker program that would have given even those who had entered illegally a chance at eventual citizenship. Even members of his own Republican Party could not agree.
Many sought to impose criminal penalties for unapproved entries and a wall along much of Mexico's 3,000 kilometer (2,000 mile) US border, measures that were approved in the House of Representatives.
In the end, Senate action was deadlocked on April 7, but will take up the matter next week.
Since then, the US state of Georgia enacted one of the toughest immigration laws in the United States, requiring employers to verify the status of workers before hiring them and penalizing those who hire undocumented workers.
The law requires employers to verify immigration status for anyone seeking state social benefits, public jobs or government contracts, with possible 20 year sentences for non-compliance.
Immigrants' rights advocates have also turned up the heat, announcing a May 1 Great American Boycott: no work, no shopping, no school.
Democratic New Mexico Governor Bill Richardson said the recent mass protests were "bigger than the civil rights movement in the '60s.
He said the historic protests put pressure on US lawmakers who are considering election-year reforms in immigration laws.
In 2003, US officials arrested 250 undocumented workers at a Wal-Mart night cleaning service in 21 states.