A newspaper reported Sunday that a British company was closed after being caught in an apparent attempt to sell black-market weapons-grade uranium to Iran and Sudan. The Observer said it could not identify the company for legal reasons, and Britain's Foreign Office declined to discuss the report, saying it never comments on intelligence and security matters. The paper said a 20-month investigation by Britain's MI6 and MI5 spy agencies and the Customs and Excise office tracked a group of Britons who allegedly obtained weapons-grade uranium from Russia's black market in an apparent plan to export it to Iran via Sudan. The alleged plot was disrupted in early 2006 before the nuclear material reached its final destination, The Observer said. One unidentified person has been charged with attempting to proliferate "weapons of mass destruction," and several other Britons believed to have links with Islamic terrorists overseas remain under surveillance, the paper said in its front-page story. It quoted an unidentified Customs and Excise spokesman as saying British officials continue to investigate allegations related to the supply of nuclear components and the activities of British nationals. Last week, the Group of Eight industrialized nations warned Iran that it could face more sanctions over its controversial nuclear program. Iran has rejected demands that it suspend uranium enrichment, which can be used to generate energy and to create nuclear weapons. The United States and some of its allies fear that Iran is pursuing a nuclear weapons program under cover of its civilian nuclear activities. Iran denies that and says its program is aimed at peaceful purposes such as generating electrical energy.