Swift workers and minority advocates told of the emotional turmoil felt during the raids.

"Our nation has no real comprehensive immigration policy, so instead we use scare tactics to mark the failure of our system," Vilsack said.

Vilsack and others alleged that immigration officials used humiliation, opposite-sex searches and long periods of secrecy in the Dec. 12, 2006, raids at Swift & Co. in Marshalltown, where 90 people were arrested on immigration charges.

Vilsack, a Democrat, alleged that federal officials violated Fourth Amendment rights, which guard against unreasonable searches and seizures.

"We're here today because it is clear that our constitutional rights have been violated during raids conducted by our government," Vilsack said.

The event was the first in Iowa and the third in the nation to be staged by the National Commission on ICE Misconduct, a group organized by the United Food and Commercial Workers International Union.

The group, of which Vilsack is a member, is examining the actions of Immigration and Customs Enforcement, an agency of the U.S. Department of Homeland Security. The commission, which is not affiliated with any branch of government, will produce a public report on its findings.

Swift workers and minority advocates described the ways in which federal officials treated the workers. One man who worked in a Colorado plant said he was denied food, water and permission to use a restroom. Some, according to secondhand accounts, were separated from their families for more than a week and, at times, were denied access to attorneys.

ICE spokesman Tim Counts said the allegations were untrue.

"All the allegations are absolutely false, including that one," Counts said of the statement from one man who said ICE officials denied him access to a restroom for about four hours. "Our work site operations are conducted fully within the law and policy, using methods that have been upheld repeatedly by courts. They're the same methods we've been using for decades."

ICE officials did not attend Tuesday's event.

Melissa Broekemeier, a 19-year employee of the Swift plant who was born in the United States, said she was detained for about six hours. Several Latino teenagers who wouldn't give their last names talked about being left to care for younger siblings after their parents were taken away.

"It would appear that ICE makes its own rules and enforces them in its own ways," said the Rev. Barbara Dinnen, a United Methodist minister who worked closely with many of the families affected by the raids.