It's been a year since US and British agents boarded a German ship in the Mediterranean Sea that led to the exposure of the unimaginable: a vast black-market nuclear arms bazaar operating under superpower radar for more than a decade.
Today, investigators from the International Atomic Energy Agency (IAEA) and some 20 countries working together have uncovered many parts of the clandestine network run by the father of Pakistan's nuclear weapons program, Abdul Qadeer Khan. Just in the past month, three more people who allegedly acted as middlemen were arrested in South Africa.
The records confiscated from these men's companies, together with other confiscated documents and information from Dr. Khan and his top aides, have led to the virtual shutdown of the clandestine network.
But government officials and experts say that in today's world, where both major presidential candidates say nuclear proliferation is the nation's most critical security threat, much more needs to be done.
"Overall, the Khan network is the biggest nonproliferation disaster of the nuclear age," says Matthew Bunn, a nuclear expert at Harvard University's John F. Kennedy School of Government. "It is certainly good news that at least the beginning of breaking up that network has occurred. Unfortunately, a substantial number of players in that network are still walking around free people."
Those walking free are probably additional businessmen, still unidentified, with specific technical capabilities to manufacture parts for centrifuges, the machines used to enrich uranium, a necessary ingredient for a nuclear bomb.
Moreover, Dr. Khan and his top aides remain free, or at least semi-free. Although Khan publicly admitted his guilt this past February, Pakistani President Pervez Musharraf pardoned him. Khan is said to be under house arrest in five costly mansions. His top aides are free as well, their movements apparently monitored.
Neither US nor IAEA investigators have been given access to Khan and his aides - a huge problem, investigators say, because they need to know if other countries besides Libya, North Korea, and Iran were offered Khan's plans and/or technology. For example, investigators in Iraq found records indicating that before the 1991 Gulf War, Khan offered Saddam Hussein, through a middleman, the same blueprints that he provided Libya.
Pakistani officials have interviewed Khan and his aides, and have "provided some information," says a Western diplomat close to the IAEA. "But they could provide much more."
Far more useful, say experts familiar with the network, have been documents confiscated in the raids on the various companies tied to the network - in Germany, Switzerland, Turkey, Malaysia, Dubai, and South Africa.
The IAEA, the nuclear watchdog arm of the United Nations, has no leverage on Pakistani officials. The United States is widely seen as the only country with the clout to pressure Pakistan.
But Washington walks a fine line with Islamabad: It must avoid alienating the country, since it's crucial to the US war on terror. At the same time, however, by backing the Musharraf regime too much, the US could inflame Islamic radicals in the country, leading to the government's overthrow. Relations between the two nations are tenuous.
Still, on balance, many experts think the US could do more to persuade Pakistan to let IAEA investigators interview Khan. "For the US to leverage Musharraf so the IAEA could talk to Khan, how does that destabilize Pakistan?" asks David Albright, president of the Institute of Science and International Security in Washington.
US government officials, for their part, won't talk about how much information Musharraf has handed over, nor how much pressure they are applying. A CIA official said the State Department is the government's focal point for tracking the network. Secretary of State Colin Powell has only said he's speaking with Musharraf, who is cooperating.
Still, investigators and officials are concerned that Khan's plans and technology may have been passed to other unknown people or countries.
One top concern: Critical parts for the centrifuge remain unaccounted for, even though individuals and companies in some 30 countries have been apprehended and searched, IAEA officials say. That suggests that other companies or people, still not caught, may be able to produce the missing parts.
"There's no sense that all the information this network possessed - gas centrifuge or nuclear weapons design or fabrication - has been recovered," says Dr. Albright. "It's still out there and could be offered to others."
"The most disturbing sign found in Libya was the bomb blueprints," says the Western diplomat close to the IAEA. "Is there some hard disk somewhere that has all these designs and where are they?"
Melissa Fleming, an IAEA spokeswoman, says an intensive probe is under way. "We need to determine who all the players were, what was involved, who the customers were, and to what extent it has now been busted or contained."