The largest investigative arm of the DHS is the Immigration Customs Enforcement Agency, also known as "ICE." Its mission is to to promote homeland security and public safety by enforcing U.S. federal criminal and civil laws concerning border control, customs, trade, and immigration.
ICE was created following the terrorist attack on the United States on September 11, 2001. At that time, the U.S. government restructured its handling of investigating and managing immigration and related activity around the world. The idea was to better protect the United States from terrorist and security threats. The Department of Homeland Security (DHS) was created in 2003 as part of this government reorganization.
ICE's most visible role, however, tends to be arresting undocumented persons within the U.S., conducting immigration raids, and overseeing immigration detention centers.
Within the ICE agency, there are two notable areas of operational focus: enforcement/removal and investigation.
This division of ICE handles primary enforcement matters to do with non-citizens in the U.S., such as apprehending people who are unlawfully present or have violated U.S. law, with a particular focus on criminals and gang members and those who have reentered the U.S. after a previous deportation.
HSI is the DHS's investigative arm, with offices in numerous U.S. cities and worldwide. It handles transnational criminal investigations, with a focus on protecting U.S. national security. HSI helps apprehend and punish people and criminal organizations seeking to exploit U.S. customs and immigration laws and procedures.
HSI has broad powers when it comes to these investigations, and addresses a range of crimes, such as financial crimes, cybercrimes, child exploitation and sex tourism, illegal weapons trade, export violations, commercial fraud, intellectual property theft, human smuggling and trafficking, narcotics smuggling and trafficking, identity and benefit fraud, human rights violations, transnational gang activity, counterterrorism, and visa security.
The ICE website, www.ice.gov, offers important information such as a "detainee locator" (for people whose non-citizen family members have been arrested by ICE; though information is not always reliable, and will be provided only for those who are 18 or over); a place to report suspicious activity (on the HSI Tip Form); and statistics on ICE's removal of aliens and enforcement activities.