The Sensex at the Bombay Stock Exchange fell 125 points, or 0.8 per cent, to 16,051 in opening trade, on Thursday morning. Later, the Sensex remained weak, and stood 144 points, or 0.9 percent in negative territory, at 16,032 in afternoon trade, a short while ago. At one stage the Sensex had slipped below the 16,000 mark. Stocks fell after IT major, Infosys plunged after declaring its third quarter results, and as investors booked profits after recent gains. Key stock indices in Japan, Taiwan, China, Hong Kong, South Korea, and Singapore were trading mixed, today. Over in the US, the Dow Jones Industrial Average had lost 0.1 per cent, overnight.