CHICAGO, May 12 (Reuters) - U.S. immigration agents said on Monday that more than 300 people were arrested at Agriprocessors Inc's kosher meat plant in Postville, Iowa, for "administration immigration violations."

"This is the largest operation of its type ever in Iowa. Agents and officers from federal, state, and local agencies are involved today," U.S. District Attorney Matt Dummermuth said in a statement on Monday.

The raid by Immigration and Customs Enforcement on the plant, reported earlier on Monday, was related to searches for aggravated identity theft, fraudulent use of Social Security numbers, people illegally in the United States, and other crimes, immigration officials said.