A Western diplomat said on Monday that a company in Dubai close to the father of Pakistan's nuclear programme "appears to have been the main player in the nuclear black market and handled the orders, procurement and shipping".
Diplomats added the Dubai-based network, which UN International Atomic Energy Agency chief Muhammad al-Baradei has described as a supermarket for countries seeking nuclear weapons, shopped for many of its supplies in Europe.
The IAEA has already questioned at least two former employees of a German company as part of its investigation into how Iran skirted sanctions to build a uranium-enrichment gas centrifuge programme, the diplomats said.
Enrichment is the purification of uranium for use as fuel in nuclear power plants or, when highly-enriched, in bombs.
Experts say getting bomb-grade material is the biggest hurdle countries with nuclear weapons ambitions must overcome.
The UN probe identified people or firms from Germany, the Netherlands, Belgium, Sri Lanka, Switzerland, South Africa, Japan, Dubai, Malaysia, the United States, Spain, Russia, China and Pakistan.
"The circle of European countries named (as being involved in the global nuclear black market) is going to get wider. There are a number of Germans whose names are being mentioned."
"The circle of European countries named is going to get wider," predicted one Western diplomat. "There are a number of Germans whose names are being mentioned."
However, he said there were so many branches of the black market that it was difficult to say who was doing what.
"It's clear that there was a person or persons masterminding the whole thing," the diplomat said. "It was very well organised and I don't think most suppliers knew who the end users were."
The black market's key middleman appears to have been a Sri Lankan businessman in Dubai.
However, the IAEA is also looking at four Germans who might have helped Iran acquire enrichment technology that could be used in an arms programme.
At least two of the people the IAEA has questioned are former senior employees of the German firm Leybold Heraeus, a leading maker of vacuum technology.
Only one of the Germans on the IAEA list is now living in Germany.One resides in the Netherlands, another is in Switzerland and the fourth is dead.
One diplomat called the man in Switzerland Germany's "most significant" suspect.
One German on the list is former Leybold sales manager Otto Heilingbrunner, who said he was surprised at being named a suspected middleman in the IAEA investigation.
Heilingbrunner, now retired and in poor health, said he was in Iran in the 1980s to help arrange the sale of equipment used to manufacture aircraft parts. He denied being a middleman.
In the 1980s, Heilingbrunner and fellow Leybold executive Gotthard Lerch, now living in Switzerland and on the IAEA list, were probed by German authorities, German sources said. Proceedings halted in 1990 for lack of evidence.
Leybold officials had no immediate comment when contacted.
Without giving details, Heilingbrunner also said that while at Leybold he travelled to Dubai on business.
number of countries known or widely suspected to be interested in nuclear weapons - Iraq, Saudi Arabia, Syria and Libya.
Khan admitted leaking Pakistani
He also visited a
The news comes after Abd al-Qadir Khan, the father of Pakistan's nuclear programme, publicly confessed last week to leaking nuclear secrets.
President Pervez Musharraf swiftly pardoned Khan, who remains a national hero in the country.
Libya admitted in December it had sought nuclear, chemical and biological weapons and agreed to let experts from the United Nations, the United States and Britain disarm it.
Meanwhile, the United States believes North Korea may have atomic weapons already.
And Washington says Iran's enrichment programme is a front for developing an atom bomb. Iran rejects the accusation.