WASHINGTON — Suspicions about massive identity theft prompted U.S. Immigration and Customs Enforcement officials to raid Swift & Co. plants in Utah and five other states, Homeland Security Secretary Michael Chertoff said Wednesday.

ICE made 145 arrests Tuesday in Utah as part of a total of 1,282 arrests made in what Chertoff called "Operation Wagon Train: the largest work-site enforcement to date." Arrests also were made in Texas, Colorado, Nebraska, Minnesota and Iowa.

Utah had the highest number of criminal arrests of illegal aliens, with 31 out of a total of 65 such arrests made in the six states. The remaining 114 arrests in Utah were for administrative matters related to their immigration status, according to ICE. The investigation is ongoing.

Those under administrative arrest had no proper documentation to work in the United States, while those with criminal charges are accused of illegal activity such as forgery, on top of not having proper visas to work here, according to the department.

No charges have been filed against Swift & Co., a beef and pork processing company that employs more than 1,000 people at its Cache County plant, according to the Department of Workforce Services.

Calls to Swift and Co. were referred to Vice President Sean Mucus, who did not return phone calls for comment Wednesday.

The company is one of 12,526 using the federal Basic Pilot program to verify employment eligibility at 45,930 sites nationwide. Chertoff said that by participating in the pilot program, the company did attempt to avoid hiring illegal workers.

In a statement Wednesday, Swift said it was able to resume operations at all six facilities after the raids but at reduced levels. The company said it expects no adverse long-term impacts to its operations.

Anti-illegal immigration activist Alex Segura, who heads the Utah Minuteman Project, was disappointed that Swift doesn't face charges. He said it's unlikely that Swift had no idea of the legal status of the employees. He said the raid indicates a need to mandate the program and to legislate better oversight.

"The program itself and the intent is a good thing," Segura said. "But I think (companies) will read what's happened to sign up for Basic Pilot to attempt to shield themselves."

Swift had filed a request for a court injunction on Nov. 28 to stop the raid. The company had learned about it in advance but was ordered not to inform workers. A federal judge dismissed the injunction request Dec. 7, allowing the raid to proceed.

A day after his wife was arrested in the Hyrum raid at Swift & Co., Tony Ivarra hadn't heard about her. The couple has a 9-year-old daughter.