The BSE benchmark Sensex today fell by nearly 266 points in the afternoon trade, due to fresh selling by funds in the absence of any positive trigger, amid a mixed trend in Asian markets.The 30-share index, which had moved down by 90 points in early trade, was further down by 176 points or 1.53 per cent to trade at 17,096 during noon.The wide-based National Stock Exchange Nifty declined by 83 points, to 5,195.In Asian markets, Hong Kong's Hang Seng index was down by 0.08 per cent, while Japan's Nikkei index gained 0.29 per cent in morning trade.