Video (00:56) : A large federal law enforcement operation conducted Wednesday targeted businesses in Minnesota and Nebraska that officials say knowingly hired - and mistreated - immigrants who are in the U.S. illegally.

Christensen Farms, a family-owned pork producer based in Sleepy Eye, Minn., was one of about a dozen businesses raided by federal immigration officers Wednesday for allegedly hiring and mistreating workers suspected of being in the country illegally.

The operation was led by U.S. Homeland Security Investigations, the investigative arm of Immigration and Customs Enforcement, and targeted agricultural firms in Minnesota and Nebraska accused of exploiting workers for profit.

Christensen Farms is one of the largest pork producers in the country, with nearly 1,000 employees and firms in several Midwest states. Search warrants were served at the company’s Sleepy Eye headquarters, as well as locations in Appleton, Minn., and Atkinson, Neb.

Company spokeswoman Amber Portner told the Associated Press that the company was cooperating with ICE and that she knew of no arrests made at company locations Wednesday.

In all, authorities issued arrest warrants for 133 workers suspected of being in the country illegally in Minnesota, Nebraska and Nevada, according to ICE, in addition to 17 individuals connected to the alleged conspiracy.

“These targeted businesses were knowingly hiring illegal workers to unlawfully line their own pockets by cheating the workers, cheating the taxpayers and cheating their business competitors,” Tracy Cormier, the special agent in charge of the operation, said in the release.

An ICE bus pulls out of a tomato plant in O'Neill, Neb., after an immigration raid at the plant Wednesday, Aug. 8, 2018. A large federal law enforcement operation conducted Wednesday targeted businesses in Nebraska and Minnesota that officials say knowingly hired - and mistreated - immigrants who are in the U.S. illegally.

ICE said the operation was part of a 15-month investigation of companies accused of employing immigrants who come to the country illegally.

“These illegal aliens were allegedly required to cash their paychecks at an illegal remittance business for a fee, have tax money deducted from their pay even though this money was never paid to the government and were coerced to remain quiet about this criminal activity,” an ICE news release said.

Those arrested were placed in custody until their cases are processed. Some will get notices to appear before an immigration judge and released, while others will stay in ICE facilities until court proceedings.

Brad Sigal, an activist from the Minnesota Immigrant Rights Action Committee, called the raid “cruel and unnecessary.”

“You can’t just look at the Trump presidency and see this as an isolated case — that suddenly he cares about the rights of workers,” he said. “This is just one more attack on the workers, whose lives are going to be dramatically worsened by this.”