VIENNA, May 12: Nuclear inspectors have found traces of highly enriched uranium at a site where Iran has denied such sensitive atomic work, diplomats said on Friday.

The diplomats said the particles of weapon-grade uranium came from sample swipes inspectors from the Vienna-based UN nuclear watchdog made last January at the Lavizan-Shian site in Tehran.

A physics research centre was dismantled and topsoil removed in 2004 after suspicions were raised about activities at the site.

“They have found particles of HEU (highly enriched uranium) but it is not clear if this is contamination from centrifuges that had been previously found (from imported material) or something new,” said one diplomat close to the UN International Atomic Energy Agency (IAEA).

If it was new, it would show Iran was hiding its own work on making highly enriched uranium.

Two other diplomats said the HEU, which is in microscopic amounts, was from vacuum pumps and that the Iranians were very nervous about the finding.

“There is something there,” said one diplomat, who did not provide further details.

Inspectors from the IAEA have found HEU particles as well as low enriched uranium, which can be used for nuclear fuel but is not refined enough for weapons use, on centrifuge equipment at several sites in Iran.

The IAEA has been investigating Iran since 2003 and says it is not yet able to certify that its nuclear program is strictly peaceful.

Iran says its nuclear program is a peaceful drive to generate electricity but the United States says it is a cover for the secret development of atomic weapons.

Centrifuges arranged in production lines called cascades enrich uranium for nuclear reactor fuel, or in highly

refined form, for atomic bomb material.

Tehran has said the enriched uranium already found was contamination from equipment acquired abroad and not the product of its own work.

Iran has since April 11 been enriching uranium at a centrifuge cascade in Natanz, but only to levels of up to five per cent enriched, which is far below the 20 per cent level considered to be HEU.—AFP