Bird's-nest restaurant chain operator United Power Investment has seen controlling shareholders sell part of their interest in the company to a mainland government tobacco unit. Substantial shareholderes Cheung Kam-wong, Tsoi Pun-pun and Cheung Chi-chung sold 40 per cent of their United Power International, which in turn holds 51 per cent of the company. The buyer is a Hong Kong-incorporated offshoot of the mainland government's tobacco bureau.