The International Atomic Energy Agency has demanded that Iran explain evidence that it has experimented with advanced nuclear warhead technology, The Guardian reported overnight Thursday. According to the report, the technology, called "two-point implosion," is considered to be a secret in the US as well as the UK. It allows development of smaller, simpler warheads, which are easier to place on missiles than older designs. The British paper reported that, according to an IAEA dossier, Iran may have experimented with the technology. Nuclear experts interviewed by the paper described the development as "remarkable" and "breathtaking," explaining that this could indicate a far more ambitious and possibly more advanced nuclear weapons program than previously thought. In an interview with the New York Times published Thursday, IAEA chief Mohamed ElBaradei said inspectors from the UN nuclear watchdog found "nothing to be worried about" at Iran's recently-revealed uranium enrichment site at Qom. ElBaradei said that the site was built as a back-up, in case the enrichment plant at Natanz was destroyed. "The idea was to use it as a bunker under the mountain to protect things," he was quoted as saying. "It's a hole in a mountain." The Times said that the IAEA would release its full report on the site inspection in mid-November. ElBaradei's comments came two days after Military Intelligence chief Maj.-Gen. Amos Yadlin told the Knesset's Foreign Affairs and Defense Committee that the Qom site had "no possible civilian use." He said that the facility was designed for the enrichment of uranium, and at full capacity can hold 3,000 advanced centrifuges. The revelation of the previously clandestine plant under construction near Qom increased concerns by the United States, France and other powers that Iran may be enriching uranium for use in nuclear weapons. Iran insists its nuclear program is strictly civilian, for research and energy purposes, and Iranian President Mahmoud Ahmadinejad has claimed that the facility was built solely for peaceful purposes. Rebecca Anna Stoil and AP contributed to this report

'Signs Iran tested advanced nuke tech'

IAEA Nothing to worry