The Department of Homeland Security has recently alerted law enforcement officials to a danger along U.S. borders: illicit tunnels.
"Tunnels under U.S. borders with Canada and Mexico serve primarily as conduits for transporting illegal drugs in the United States," the threat assessment says. "In addition, reliable reporting indicates that some tunnels also are used for alien smuggling, including special interest aliens."
The only U.S.-Canada tunnel discovered to date was located at Lynden, Wash., and Aldergrove, British Columbia, just east of a legitimate port of entry. It served as a "conduit" for illegal drugs. (Unclassified Government Photo)