The Sensex at the Bombay Stock Exchange was trading 175 points in the positive territory at 19,355 in late morning trade, when reports last came in. The 30-share index extended gains for the fourth-straight day and rose by 144 points in early trade today. It had gained over 448 points in the previous three sessions.The Nifty at the National Stock Exchange moved up by 64 points to 5,901.