Vienna  - The International Atomic Energy Agency (IAEA) has detected more traces of uranium as well as graphite in samples taken at an alleged Syrian nuclear reactor site, an IAEA report and a senior UN official said on Friday.

While uranium is used to fuel certain reactor types, graphite can serve as a construction element in the reactor core.

"We are sure it's man-made," the UN official said about the graphite. This finding was not included in the report as the IAEA had not yet determined if the material was of the type used in nuclear installations, he said.

Last June, IAEA inspectors took samples a the al-Kibar site in the Syrian desert, which was bombed by Israel in 2007.

The United States has alleged the installation was a nuclear reactor, but Syria insists that Israel hit a conventional military facility.

The IAEA had now found 80 particles of man-made uranium, the official said. "We have found nuclear material at the site and Syria has to explain where that material came from," he said.

The report by IAEA Director General Mohamed ElBaradei said that "the Agency's current assessment is that there is a low probability that the uranium was introduced by the use of missiles" from Israel, as Syria has alleged. dpa