:BYD Co shares sank nearly 12per cent on Tuesday after a large stake matching the size of Berkshire Hathaway Inc's investment in the Chinese electric car company appeared in Hong Kong's clearing system. The development prompted speculation that Warren Buffett's company might be reducing its multi-billion-dollar stake in BYD. A 225 million share BYD stake entered Hong Kong's Central Clearing and Settlement System, with Citigroup Inc serving as custodian. Berkshire acquired its own 225 million BYD shares in 2008, giving it a 7.73per cent stake, according to BYD's annual report. The stake also represents 20.49per cent of BYD's total issued...