CEDAR RAPIDS, Iowa (AP) -- Federal immigration agents on Monday arrested more than 300 people in Postville during a raid at the nation's largest kosher meatpacking plant.
The raid by agents from U.S. Immigration and Customs Enforcement was the largest in Iowa history, said Matt M. Dummermuth, U.S. attorney for the Northern District of Iowa.
Dummermuth said the raid at the Agriprocessors Inc. plant in northeast Iowa came after months of planning, beginning in October 2007. Federal agents were helped by state and local police.
Authorities said more than 300 workers were arrested and charged with immigration violations.
''Can't speculate on if that number will go up,'' said Claude Arnold, special agent in charge of ICE's office in Bloomington, Minn. ''We'll have more information on that tomorrow.''
Of those arrested, 44 were released for humanitarian reasons, primarily because they must care for children. Those released were ordered to report to court later.
The detainees were held in local jails or driven by bus about 75 miles to the National Cattle Congress fairgrounds in Waterloo. Federal authorities previously leased the fairgrounds and have turned it into a secure center.
People arrested will be fed three meals a day, plus an evening snack, Arnold said. All those taken to the fairgrounds should be moved to other sites by Thursday.
Authorities arrived at the Agriprocessors plant about 10 a.m. and presented company officials with search warrants. Agents asked to speak with all the employees, and plant officials cooperated and shut down their operations.
Some have criticized a December 2006 immigration raid at a Swift & Co. meatpacking plant in Marshalltown, part of a larger action in Iowa, Nebraska and four other states. Asked if Monday's action differed from previous raids, officials said no.
''We're doing things the way we always do,'' Arnold said. ''Standard operating procedure. We're doing things the right way.''
The raid was aimed at seeking evidence of identity theft, stolen Social Security numbers and for people who are in the country illegally, ICE spokesman Tim Counts said.
According to an affidavit and search warrant, authorities relied heavily on an informant who infiltrated the plant with documents provided by ICE. The informant was hired in January and wore recording devices monitored by ICE.
The informant allegedly witnessed a system where some employees were paid in cash or with checks that did not have Agriprocessors' name on them.
Counts said a toll-free telephone number had been set up to assist family members of those arrested who have questions about their detention status and the removal process.
Sister Mary McCauley, a Roman Catholic nun at St. Bridget's Catholic Church in Postville, said family members of plant workers came to the nearby church in tears.
''The people right now are hearing and seeing the helicopters,'' McCauley said Monday morning. ''They are just panic-stricken and very frightened and some of them are coming to the church as a safe haven.''
The church is about five blocks from the plant, she said.
She said rumors began swirling around the community on Friday about an upcoming raid, leaving many people worried.
She said immigration officials arrived with buses, vans and two helicopters.
She said she went to the plant to help provide information and assist workers but was not allowed to get close.
''Some of the people that are going to be detained are up against a fence and now they're tying their hands,'' she said.
Many of the plant workers are Hispanic, mostly from Mexico and Guatemala, she said.
Asked about the raid during a Monday news conference, Gov. Chet Culver said both illegal immigrants and companies that knowingly hire them should be prosecuted.
''Illegal means illegal, not just those who are crossing the border illegally but those who are responsible for helping to make it happen,'' Culver said.
Culver added the importance in taking humanitarian concerns into account and said he'd raised this issue with immigration authorities.
The governor said he'd been told last week there would be federal action.
Agriprocessors also operates a slaughterhouse in Gordon, Neb. Counts said there was no raid at that facility on Monday.
Associated Press writers Michael Crumb, Mike Glover and David Pitt in Des Moines, Iowa, contributed to this report.