"This Office of Immigration Statistics Annual Report presents information on the apprehension, detention, return, and removal of foreign nationals during 2006 as well as investigations of individuals or organizations in violation of immigration laws. [...] DHS apprehended more than 1,206,000 foreign nationals. Nearly 88 percent were natives of Mexico. There were 8,778 ICE Office of Investigations criminal arrests and 6,872 convictions for immigration-related crimes. ICE detained approximately 257,000 foreign nationals. There were 272,389 aliens removed from the United States. The leading countries of origin of those removed were Mexico (67 percent), Honduras (10 percent) and Guatemala (7 percent). More than 1,043,000 other foreign nationals accepted an offer to return to their home countries without a removal order. Expedited removals accounted for 110,147 or 40 percent of all removals. DHS removed 95,752 known criminal aliens from the United States."
United States Department of Homeland Security: http://www.dhs.gov/