The Bombay Stock Exchange benchmark Sensex fell by around 70 points on Thursday as funds and retail investors indulged in booking profits amid weak Asian markets.The Sensex, which had lost 51.87 points in yesterday's choppy trade, moved further down by 70.68 points to 16,928 in early trade. The wide-based National Stock Exchange index Nifty also drifted by 18.65 points to 5,036.