VIENNA, Austria (AP) _ An investigation of the black market supplying nations wanting nuclear arms has spread to more than 20 firms _ some of them North American _ the chief of the U.N. atomic agency told The Associated Press Friday. A senior diplomat identified one of the firms as U.S. based.

Demanding anonymity, the diplomat also said the Syria and Saudi Arabia are also being investigated as possible buyer nations, beyond Iraq, Iran, Libya and North Korea _ the countries known to have been in contact with Pakistani scientist A.Q. Khan and members of his procurement network.

But the diplomat, who is familiar with the Vienna-based IAEA told The AP that beyond suspicions prompting a continuing investigation, ``there has been no proof'' on Syria and Saudi Arabia that would warrant them being reported to the board of governors of the International Atomic Energy Agency.

In separate comments to The Associated Press, IAEA Director General Mohamed ElBaradei avoided specifics on the locations of the firms supplying the nuclear black market beyond saying there were ``over 20 countries, some of them in North America.''

The diplomat said at least one of them was in the United States. He declined to elaborate, saying the agency ``was not yet at the bottom of that story.'' But he said what is known about that company sheds new light on the activities of the network, known up to now for primarily supplying technology to North Korea, Libya and Iran as part of the process allowing them to make enriched uranium that can be used either to generate electricity or make weapons.