AlHijjah 17, 1432, Nov 13, 2011, SPA --The U.S. National Transportation Safety Board has sent a team of investigators to Mexico to probe the helicopter crash that killed the country's No. 2 official, AP reported. The board said that it has also sent representatives of the Federal Aviation Administration to investigate Friday's crash in a rural area south of Mexico City. The crash killed Interior Minister Francisco Blake Mora and seven others. The safety board said in a news release Sunday that Mexico requested help. The agents arrived Saturday. President Felipe Calderon has asked Mexico's transportation secretary to carry out a thorough investigation into the causes of the helicopter crash. Mexico's Transportation and Communications Department will remain the lead investigative agency.