The Sensex at the Bombay Stock Exchange remained weak in afternoon trade, and stood 49 points, or 0.2 percent in negative territory, at 20,842 a short while ago. Earlier in the morning, the Sensex had dropped 28 points, or 0.1 per cent, to 20,863 on profit-booking by funds after recent strong gains, amid mixed Asian bourses. The Sensex had rallied almost 700 points in the previous three trading sessions. Stock markets in Japan, China, Hong Kong, Taiwan, Indonesia, Singapore and South Korea were trading mixed, today. The US Dow Jones Industrial Average had ended 0.1 per cent lower in yesterday's trade.