The benchmark Sensex, which opened 52 points down, fell by another 140.23 points at midsession on BSE on Thursday as funds reduced their holding in heavy-weight counters, influenced by weak Asian trend.
The Sensex declined by 140.23 points at 1330 hrs on heavy selling in stocks like Tata Steel, Reliance Industries and Infosys Technologies.
The second wide-based index, Nifty, fell by 42.35 points, or nearly one per cent, at 4203.85. It had opened 13.85 points down at 4222.35.
The selling pressure gathered momentum after a fall in Chinese and other Asian stock markets.