USA - Warren Buffett's Berkshire Hathaway has sold another massive stake in Bank of America - raising red flags in an ominous sign for Wall Street investors. The Omaha-based financial conglomerate has seen its stake in BofA fall by around 150 million shares, bringing the total sales since mid-July to nearly $5.4 billion. Berkshire has traditionally been bullish on financial companies, leading some analysts to call Buffett's sell-off a clear warning that tougher times may lie ahead. BofA has been Buffett's most favored stock over the last seven years and the bank's largest single shareholder. His selling of such a large number of shares over such a short period of time could suggest that economic turbulence or further market turmoil is on the way.