U.N. investigators have found traces of uranium at a Syrian site Washington claims was a secret nuclear reactor almost built before Israel bombed the target last year, diplomats said on Monday.
They said the minute uranium particles turned up in some environmental swipe samples U.N. inspectors took at the site in a visit last June. They said the finding was not enough to draw conclusions but raised concerns requiring further clarification.
The International Atomic Energy Agency and Syria had no immediate comment.
However, word of the finding leaked hours after IAEA officials confirmed Director Mohamed ElBaradei was preparing a formal written report on Syria for the first time.
Moreover, Syria has been made an official agenda item at the year-end Nov. 27-28 meeting of the U.N. watchdog's 35-nation board of governors, unlike previously when IAEA officials said initial inquiries were inconclusive.
Syria denies U.S. intelligence alleging it was building a reactor with North Korean expertise meant to make plutonium, the main atomic bomb ingredient reprocessed from spent uranium fuel.
Damascus says the unverified intelligence was fabricated and Washington has no credibility in the field after using bogus evidence of an Iraqi doomsday arms programme to justify the 2003 invasion that ousted Saddam Hussein and devastated the country.
Syria has also said it would grant IAEA investigators full transparency as long as its national security is not endangered.
"We would like to underline that my government is cooperating with the agency in full transparency and will follow suit all along the way," Ibrahim Othman, Syria's Atomic Energy Commission director, told the IAEA in October.
ElBaradei told an IAEA board meeting in September that preliminary findings from test samples taken by inspectors granted a visit in June to the desert location hit by Israel bore no traces of atomic activity.
Diplomats accredited to the Vienna-based nuclear watchdog said a wider range of samples had now been analyzed and some showed contamination with minute amounts of a uranium compound.
"It isn't enough to conclude or prove what the Syrians were doing but the IAEA has concluded this requires further investigation," said one diplomat accredited to the IAEA.
Syria's only declared nuclear site is a research reactor.
ElBaradei's Syria report, and his latest Iran one, are expected to be issued next week ahead of the board meeting.