Bordering On Nukes?

A key al-Qaeda operative seized in Pakistan recently offered an alarming account of the group's potential plans to target the U.S. with weapons of mass destruction, senior U.S. security officials tell TIME. Sharif al-Masri, an Egyptian who was captured in late August near Pakistan's border with Iran and Afghanistan, has told his interrogators of "al-Qaeda's interest in moving nuclear materials from Europe to either the U.S. or Mexico," according to a report circulating among U.S. government officials.

Masri also said al-Qaeda has considered plans to "smuggle nuclear materials to Mexico, then operatives would carry material into the U.S.," according to the report, parts of which were read to TIME. Masri says his family, seeking refuge from al-Qaeda hunters, is now in Iran.

Masri's account, though unproved, has added to already heightened U.S. concerns about Mexico. Homeland Security Secretary Tom Ridge met publicly with top Mexican officials last week to discuss border security and smuggling rings that could be used to slip al-Qaeda terrorists into the country. Weeks prior to Ridge's lightning visit, U.S. and Mexican intelligence conferred about reports from several al-Qaeda detainees indicating the potential use of Mexico as a staging area "to acquire end-stage chemical, biological, radiological and nuclear material." U.S. officials have begun to keep a closer eye on heavy-truck traffic across the border. The Mexicans will also focus on flight schools and aviation facilities on their side of the frontier. And another episode has some senior U.S. officials worried: the theft of a crop-duster aircraft south of San Diego, apparently by three men from southern Mexico who assaulted a watchman and then flew off in a southerly direction. Though the theft's connection to terrorism remains unclear, a senior U.S. law-enforcement official notes that crop dusters can be used to disperse toxic substances. The plane, stolen at night two weeks ago, has not been recovered.