Actually another article speculates that Mexican gangs are being hired by AQ to smuggle in the nukes.
This Man Leads Nuclear ‘9/11' Plan NewsMax/ Friday, June 1, 2007 He is the most wanted man in America yet most Americans have never heard his name. He has been described as the "Fixer" of the Sept. 11 attacks. Several captured al-Qaida operatives have revealed this is the same man who bin Laden has tapped to lead the terror group's diabolical scheme to detonate nuclear devices simultaneously in several U.S. cities. Meet Adnan el-Shukrijumah, now believed to be operating within the U.S. – a man the FBI warns is likely armed and dangerous. The U.S. government is offering a $5 million reward for information leading to his capture.
After the terrorist strikes, Adnan became a key figure in al-Qaida's plans to escalate its attacks on the U.S. Williams compiled evidence that Osama bin Laden designated him to arrange a simultaneous nuclear attack on seven U.S. cities – New York, Washington, Los Angeles, Houston, Miami, Boston and Las Vegas." http://www.newsmax.com/scripts/printer_friendly.pl?page=http://www.newsmax.com/archives/articles/2007/5/31/211635.shtml?s=lh