The DOJ can't say what is being investigated. But it did say…
…its investigation is being "coordinated" with ICE and the US Department of Labor, as the Des Moines Register reports:
Justice Dept: Postville investigation 'continuing'
JANE NORMAN • REGISTER WASHINGTON BUREAU
Washington, D.C. – A federal investigation into the Agriprocessors plant in Postville is "continuing," according to a letter sent by a Justice Department official to Rep. Bruce Braley, a Waterloo Democrat.
The letter does not specify what is being investigated, but notes that the Justice Department is coordinating with Immigration and Customs Enforcement as well as the U.S. Department of Labor. It also says the Iowa Department of Labor was contacted before a major worksite enforcement action at the plant in May. More than 300 workers were arrested on criminal and immigration charges at the time.
Shortly afterward, Braley wrote to the Justice Department, the Department of Labor and Immigration and Customs Enforcement asking about the status of any ongoing investigations at the plant, including reported violations of workplace and child labor regulations.
He also asked if there was communication between labor officials and immigration officials prior to the action, and said he believes it is important that any investigation be continued.
In response, Keith B. Nelson, principal deputy assistant attorney general, wrote Braley that because of legal and ethical considerations, investigations cannot be discussed.
"We can confirm that the investigation that led to the recent convictions of 297 defendants detained at Agriprocessors, Inc., on May 12, 2008, is continuing," he wrote. "We can also confirm that the Department of Justice is coordinating with Immigration and Customs Enforcement and the United States Department of Labor. In addition, the Iowa Department of Labor was contacted prior to the May 12 action.