WASHINGTON — The Department of Homeland Security joined forces Tuesday with the U.S. Immigration and Customs Enforcement and U.S. Postal Inspection Service to identify major players in an international operation involving underground child pornography. In the past few years, the DHS has increased efforts to track down and arrest predators involved with child pornography. Since 2003, Homeland Security Investigations has initiated more than 29,000 cases and arrested more than 10,000 individuals for these types of crimes.