Iran Nuclear Program: U.N. Says Credible Evidence Tehran Is Working On Nuclear Weapon VIENNA â€” The U.N. nuclear agency said Friday it is "increasingly concerned" about a stream of intelligence suggesting that Iran continues to work secretly on developing a nuclear payload for a missile and other components of a nuclear weapons program. In its report, the International Atomic Energy Agency said "many member states" are providing evidence for that assessment, describing the information it is receiving as credible, "extensive and comprehensive." The restricted 9-page report was made available Friday to The Associated Press, shortly after being shared internally with the 35 IAEA member nations and the U.N. Security Council. It also said Tehran has fulfilled a pledged made earlier this year and started installing equipment to enrich uranium at a new location â€“ an underground bunker that is better protected from air attack than its present enrichment facilities. Enrichment can produce both nuclear fuel and fissile warhead material, and Tehran â€“ which says it wants only to produce fuel with the technology â€“ is under four sets of U.N. Security Council sanctions for refusing to freeze enrichment, which it says it needs for fuel only. It also denies secretly experimenting with a nuclear weapons program and has blocked a four-year attempt by the IAEA to follow up on intelligence that it secretly designed blueprints linked to a nuclear payload on a missile, experimented with exploding a nuclear charge, and conducted work on other components of a weapons program. In a 2007 estimate, the U.S. intelligence community said that while Iran had worked on a weapons program such activities appeared to have ceased in 2003. But diplomats say a later intelligence summary avoided such specifics, and recent IAEA reports on the topic have expressed growing unease that such activities may be continuing. The phrase "increasingly concerned" has not appeared in previous reports discussing Iran's alleged nuclear weapons work and reflects the frustration felt by IAEA chief Yukiya Amano over the lack of progress in his investigations. His report said that choice of language is due to the "possible existence in Iran of past or current undisclosed nuclear related activities" linked to weapons work. In particular, said the report, the agency continues to receive new information about "activities related to the development of a nuclear payload for a missile." Acquired from "many" member states, the information possessed by the IAEA is "extensive and comprehensive ... (and) broadly consistent and credible," said the report.