The Colombian government revealed last month that the country's FARC rebels were seeking to acquire enriched uranium. The rebels may have been more interested in trading the uranium to a terrorist group than in developing it into nuclear arms for their own purposes.
A stash subsequently uncovered in Colombia proved to be harmless. But the case shows that the danger of terrorist or insurgent groups acquiring nuclear materials on the black market could be a looming threat.
Terrorism experts say it points to a danger that's greater than many people realize.
Intelligence and law enforcement agencies in the United States and other countries have sought to penetrate nuclear smuggling networks through sting operations and other counter-terrorism measures but so far with limited success.
A rash of nuclear smuggling came in the 1990s, following the breakup of the Soviet Union, when many nuclear facilities weren't secure. Since then, security at those facilities and others has been greatly tightened.
But there has been an increase in threatening rhetoric from the al-Qaida leadership, directed specifically against Western Europe and the United States. And some of the nuclear material that was lost 10 years ago might only now be turning up in the black market.
Louise Shelley, who directs the Terrorism, Transnational Crime and Corruption at George Mason University, says there is a potential threat.
"I mean, when Osama bin Laden says, 'We're going to get at you,'" Shelley said, "this is the kind of point where you think that the rhetoric is escalating to something that may make sense to use this."
Much of the nuclear material, or alleged nuclear material, moving through the black market, however, involves scams. The uranium for which the Colombian rebels were reportedly willing to spend more than $2 million was useless.