On April 30, 2009, the DHS announced a new worksite enforcement strategy which focuses on targeting employers who knowingly hire illegal workers and criminal aliens. The DHS stated in its announcement that in order to target the root cause of illegal immigration, the enforcement arm of its agency, ICE will focus its resources on the criminal prosecution of employers who knowingly hire illegal workers. While ICE will continue to arrest and initiate removal proceedings against illegal workers who are found in the course of worksite enforcement actions, this will be done in a manner consistent with immigration law and DHS priorities. In addition, ICE will use all available civil and administrative tools, including civil fines and debarment, to penalize and deter illegal employment. The DHS affirmed that ICE officers will be held to high investigative standards including: investigating the mistreatment of workers, trafficking, smuggling, harboring, visa fraud, identification document fraud, money laundering, and other such criminal conduct; and obtaining indictments, criminal arrest or search warrants, or a commitment from a U.S. Attorney's Office (USAO) to prosecute the targeted employer before arresting employees for civil immigration violations at a worksite. The DHS promised that existing humanitarian guidelines will remain in effect where worksite enforcements involve 25 or more illegal workers, a reduction from the previous threshold of 150.