Iran was said to have built more than 5,000 gas centrifuges for its nuclear weapons program. Iranian opposition sources said Teheran built the centrifuges for its nuclear plant at Natanz without the knowledge of the International Atomic Energy Agency and European Union. Natanz has been the leading facility for the enrichment of uranium, a key element in the process to produce nuclear weapons. "Iran has already manufactured as many as 5,000 centrifuge machines ready to be installed in Natanz, which is a clear breach of its agreements with the IAEA and the EU," Alireza Jafarzadeh, a leading Iranian opposition figure, said.On Jan. 11, Iran began removing the seals on a 164-centrifuge cascade at Natanz. The cascade has been deemed too small for a nuclear weapons program.