Instead of moving nuclear material in armored, well-defended convoys, [Pakistan's Strategic Plans Division] prefers to move material by subterfuge, in civilian-style vehicles without noticeable defenses, in the regular flow of traffic. according to both Pakistani and American sources, vans with a modest security profile are sometimes the preferred conveyance. and according to a senior U.S. intelligence official, the Pakistanis have begun using this low-security method to transfer not merely the “de-mated” component nuclear parts but “mated” nuclear weapons.
According to Goldberg and Ambinder, the U.S. was worried enough about it to have laid out a specific contingency plan to seize or disable the country's nuclear arsenal in the event of an emergency. The 10,000-word story also reveals details about Admiral Mike Mullen's falling out with Pakistan after learning of the Pakistani military's involvement in the murder of Pakistani journalist Saleem Shahzad as well as China's openness to disabling Pakistan's nuclear capabilities, an acknowledgment of how serious it considers the threat of loose nukes in Pakistan. You can read the full story here.