The United States is taking additional security precautions for air cargo, following a recently thwarted terrorist plot to send mail bombs from Yemen to the U.S. Homeland Security chief Janet Napolitano says the U.S. is extending a ban on air cargo, which is already in effect for Yemen, to include Somalia. Napolitano says toner and ink cartridges weighing more than a half-kilogram are banned on passenger planes on domestic and incoming international flights. Meanwhile, investigators are searching for more clues into the failed plot last month. Two packages containing bombs were found inside desktop computer printers on cargo flights that were shipped from Yemen bound for two synagogues in Chicago. U.S. authorities have heightened security at the nation’s airports, seaports and land border crossings. VOA's Chris Simkins reports.