Vienna, Austria ? More than 20 firms — including at least one American company — have supplied rogue nations seeking nuclear arms, marking the first time a U.S. company has been linked to the black market network.

International Atomic Energy Agency Director General Mohamed ElBaradei, who is heading a probe into the illicit sales, avoided specifics on the locations of the companies in an interview with The Associated Press Friday.

But a senior diplomat said at least one was in the United States — the first time in five months of investigations by the U.N. nuclear agency that an American company has been implicated in the black market network headed by Pakistani scientist Abdul Qadeer Kahn.

The diplomat, who did not name any of the companies, said Syria and Saudi Arabia were being investigated as possible buyer nations, in addition to Iraq, Iran, Libya and North Korea, countries already known to have bought from or been in contact with the clandestine network.

The diplomat, who spoke on condition of anonymity, told the AP that beyond suspicions prompting a continuing investigation, “there has been no proof” that would warrant Syria and Saudi Arabia being reported to the IAEA board of governors.

Syria has been cited by the United States as trying to acquire the technology to make nuclear weapons, including centrifuges needed to enrich uranium, a charge Damascus denies.

Saudi Arabia has denied news reports that it agreed to supply Pakistan with oil in exchange for nuclear know-how as a hedge against fears that Iran was developing nuclear weapons.

Israel has good intelligence on its neighbors, but does not appear to consider Syria or the Saudis the primary nuclear threat in the region. During ElBaradei’s visit to Israel, which ended Thursday, officials repeatedly expressed concern about Iran’s nuclear ambitions, but did not mention the other two countries, according to officials familiar with the discussions in Jerusalem.

ElBaradei’s route to Israel had been kept confidential by the agency. But he confirmed Friday that he had arrived from Dubai, a major shipping and supply point used by the Khan network for clients in the Middle East and possibly some African nations.

ElBaradei said he had talked to the defense, police and foreign ministers of the United Arab Emirates on ways to block ports and other transport routes for illicit nuclear shipments.

“We will help them with updating security in the Emirates,” ElBaradei said without elaboration.