An explosives business closed for allegedly helping Iran produce weapons of mass destruction has been linked with another front company for China's official arms dealer. Throne Star was revealed by the South China Morning Post yesterday as having taken over the explosives business of Rex International Development, deregistered last year in one of the colonial government's last acts. Now it can be revealed that Throne Star has links to Silver City International, through which the mainland defence industry conglomerate China North Industries (Norinco) conducts a web of business interests. A number of Silver City directors have listed their address as 7A Yuetan Nan Street, Beijing, which is the headquarters of Norinco's marketing arm. Some directors of Silver City group companies have sat on the boards of Rex or Throne Star. They have included Norinco president Wang Liansheng. Throne Star and Silver City operate from different floors in Sheung Wan's Shun Tak centre - Throne Star International controls the lucrative explosives manufacturing operation from the 32nd floor while Silver City International (Holdings) operates from the 27th floor. The Silver City group of companies has been linked with Rex and Throne Star in property development, transport, finance and investment activities for Norinco. A mainland dynamite expert, Jiang Chengwei, is the key link between Rex and Throne Star as a director of both companies. Former Democrat legislator James To Kun-sun said the Government's handling of the issue would be a test of its independence. 'I presume that the Hong Kong Government is watching closely this company,' said Mr To, a former chairman of Legco's security panel. The Government said last night there was no agreement between it and Rex to allow another company to be formed and continue the deregistered company's operation. It said Throne Star International was incorporated in 1991, well before the winding up of Rex. Its explosives manufacturing activities were properly licensed.