RALEIGH, N.C. -- Hundreds of workers at a Smithfield Packing Co. plant have quietly left their jobs or stopped showing up for work following a crackdown on illegal immigrants employed at the world's largest hog slaughterhouse.

Many have submitted resignation letters and collected pay for unused vacation, while others identified by the company in November as having unverifiable employment documents quit without notice, company spokesman Dennis Pittman said.

In all, Pittman said about 300 employees had left the massive plant in Tar Heel on their own as of Monday.

"Some of these people had been here seven, eight or nine years. It is certainly a blow to the company," Pittman said. "It's slowing us down some. We've had to work some Saturdays and some overtime. When you have new trainees, it takes some time to get those people caught up."

In November, Smithfield sent letters to between 500 and 600 employees whose Social Security numbers, names or other personal information couldn't be verified. The company also fired about 50 workers for providing false information.

The firings spurred a massive walkout at the plant, as about 1,000 employees -- most of them Hispanic -- left in protest, quickly picking up the support of a union that has tried for years to organize the plant, where Smithfield employs about 5,000 people who slaughter up to 32,000 hogs a day.

Employees were back on the job two days later after Smithfield agreed to rehire the fired workers and meet with each letter recipient, who then received 60 days to verify their employment status.

Those grace periods began running out this month. Pittman said about 50 workers have successfully resolved discrepancies in their employment documentation and remain employed at the plant. None have been fired, he said.

The process began when federal immigration authorities approached the company after raiding a Virginia plant owned by its parent, Smithfield Foods Inc., company officials have said. Hundreds of workers were identified after Smithfield agreed to an audit of its I-9 tax forms, a requirement to join a voluntary enforcement program offered by U.S. Immigration and Customs Enforcement.

Smithfield officials have said they would prefer to keep the employees identified by the audit, but that they must abide by immigration laws. Critics called those claims empty, saying the company has known about the document discrepancies for years.

"Giving things to ICE, the company has power in that," said Leila McDowell, a spokeswoman for the Smithfield Justice Campaign, a union organizing effort. "There is concern that Smithfield is manipulating immigration laws to intimidate workers."

The United Food and Commercial Workers International Union has been trying to organize the Tar Heel plant, about 80 miles south of Raleigh, for more than a decade. Union officials accuse the company of cooperating with federal immigration authorities to quell immigrant employees who have become emboldened enough in recent months to demand better working conditions.

McDowell said the union launched an aggressive organizing campaign in June and Smithfield began working with federal authorities in July, though Pittman said the company began working with ICE last spring. Messages left with U.S. Immigration and Customs Enforcement were not immediately returned Monday.

Last month, federal agents arrested 21 people inside the plant on immigration charges. Employees were called away from the assembly line by supervisors and escorted to a conference room where they were interviewed by agents and taken into custody. Pittman said some of those workers had been identified during the company's records check, while others had not.

Production stalled the next day after about 200 workers failed to show up overnight to clean the plant, and company officials angrily blamed the labor union for enflaming fear among immigrant and Hispanic workers. Union officials said workers spread word of the arrests on their own, but they blasted Smithfield publicly for how the arrests were carried out.

There have been no other arrests at the plant since, Pittman said.

The union has also challenged a Dec. 12 raid that led to the arrest of nearly 1,300 illegal workers at Swift & Co. meatpacking plants in six states. The union believes the arrests violated the workers' constitutional rights to due process; ICE has denied the charge.

Last month, Smithfield settled a complaint tied to union elections held at the plant in 1993 and 1997. Employees voted against organizing in those elections, although a federal appeals court later found the company illegally worked to defeat those efforts.

The company will pay $1.1 million in back wages, plus interest, to workers fired as part of the dispute under an agreement reached with the National Labor Relations Board.

Following the settlement, the company asked the union to schedule a new election at the plant. The union has dismissed the offer, saying another case of unfair labor practices involving a subcontractor is still pending against Smithfield.

Union organizers also argue the recent immigrant enforcement efforts have created a tense atmosphere at the plant that would bias any election.

------

On the Net:

Smithfield Foods Inc.: http://www.smithfield.com/

U.S. Customs and Immigration Enforcement: http://www.ice.gov/

United Food and Commercial Workers: http://www.ufcw.org/