DES MOINES (AP) - The Iowa attorney general's office says investigators have executed a search warrant at the Agriprocessors Inc. plant in Postville, which was the site of a huge immigration raid in May.

The attorney general's office said in a short statement that no one was arrested Friday when the northeast Iowa plant was searched. Officials wouldn't comment on what investigators were looking for at the facility, which is the world's largest kosher meatpacking plant.

On May 12, it was the site of one of the largest single-site immigration enforcement operations in U.S. history. Federal immigration agents arrested 389 workers during the raid.

Earlier this month, the Iowa Labor Commissioner's Office said an investigation that spanned several months uncovered 57 cases of child labor law violations at the plant.

The Iowa attorney general's office said it is serving as prosecutor at the request of the Allamakee attorney's office.

The Iowa Division of Criminal Investigation and the Iowa State Division of Labor are leading the investigation.

Requests for comment from a spokesman for Agriprocessors weren't immediately returned.

Top executives and the plant's owners have not yet faced any charges in connection with the raid or alleged child labor violations. Two lower-level supervisors have pleaded guilty to immigration charges.

Earlier this week, Martin De La Rosa-Loera appeared in federal court in Cedar Rapids and pleaded guilty under an agreement with prosecutors to aiding and abetting the harboring of undocumented immigrants.

Last week, Juan Carlos Guerrero-Espinoza pleaded guilty to one count of conspiracy to hire illegal immigrants and one count of aiding and abetting the hiring of illegal immigrants.