The U.N. atomic agency has found traces of highly enriched uranium at an Iranian site linked to the country's defense ministry, diplomats said Friday. The finding added to concerns that Tehran was hiding activities that could be used to make nuclear arms.

Mohamed ElBaradei, head of the International Atomic Energy Agency (IAEA), gestures during a press conference at Schiphol airport in Amsterdam, Netherlands, Thursday, May 11, 2006. [AP]

The diplomats, who demanded anonymity in exchange for revealing the confidential information, said the findings were preliminary and still had to be confirmed through other lab tests. But they said the density of enrichment appeared close to or beyond weapons grade ¡ª the level used to make nuclear warheads.