U.S. Airports Warned About Terror Dry Runs

From U.S. Airports Warned About Terror Dry Runs:

Airport security officers around the U.S. have been alerted by federal officials to look out for terrorists practicing to carry explosive components onto aircraft, based on four curious seizures at airports since last September. The seizures at airports in San Diego, Milwaukee, Houston and Baltimore included "wires, switches, pipes or tubes, cell phone components and dense clay-like substances," including block cheese, said an unclassified alert distributed on July 20 by the Transportation Security Administration. A joint FBI-Homeland Security Department assessment found that terrorists have conducted probes, dry runs and dress rehearsals in advance of previous attacks.