In August 2002, the Iranian opposition group Mojahedin-e Khalq (MEK, a.k.a. MKO) announces that Iran is building an underground uranium enrichment facility at Natanz, and a heavy water reactor at Arak. It is widely believed that the evidence had been passed to the MEK by Israeli intelligence.
Enrichment and reactors are not forbidden to Iran as a signatory of the Nuclear Non-Proliferation Treaty (NPT), but the failure to disclose the work prompts an IAEA investigation and much closer scrutiny. Iran insists its efforts are peaceful, but is found in breach of its IAEA safeguards agreement, and accused by the IAEA of a "pattern of concealment."
2004: Then-Secretary of State Colin Powell tells reporters that Iran had been working on technology to fit a nuclear warhead onto a missile. "We are talking about information that says they not only have [the] missiles but information that suggests they are working hard about how to put the two together," he said.
2005: US presents 1,000 pages of designs and other documentation allegedly retrieved from a computer laptop in Iran the previous year, which are said to detail high-explosives testing and a nuclear-capable missile warhead. The “alleged studies,” as they have since been called, are dismissed by Iran as forgeries by hostile intelligence services.