The Bombay Stock Exchange benchmark Sensex was in red on Friday in morning trade. Sensex was down by 448 points at 16,406 while NIFTY was down 140 points at 4,864 a short while ago. Sensex tumbled over 451 points while Nifty dropped by 140.50 points in opening trade on hectic selling by funds.Brokers said the selling focus was more on banking and realty stocks after Dubai's debt problems revived concerns about the global financial system and rattled markets across Europe and Asia.