Following the release of claims that Iran has yet more secret uranium enrichment facilities than have previously been disclosed - Colin Powell (at this point still U.S. Secretary of State) was quoted as saying he'd seen similar "intelligence" and that he believed the report. Despite it coming from an Iranian dissident group which the U.S. lists as a terrorist group.
This CNN article documents a little firestorm around his comments:
Source of Powell's Iran intelligence under scrutiny
Friday, November 19, 2004 Posted: 4:15 PM EST (2115 GMT) CNN.COM