The Sensex is now down 631 points at 15,740.The NSE Nifty is down 176 points at 4,766.HDFC and HDFC Bank have plunged over 7% each to Rs 2,425 and Rs 1,300, respectively.ICICI Bank, Infosys and Hindalco have tumbled nearly 7% each to Rs 778, Rs 1,424 and Rs 164, respectively.TCS has shed 6.5% at Rs 814. ONGC has slumped 6% to Rs 988.DLF and Jaiprakash Associates have dropped around 5.5% each to Rs 657 and Rs 228, respectively.Reliance Energy, SBI, Grasim and Reliance Communications have slipped nearly 5% each to Rs 1,268, Rs 1,597, Rs 2,575 and Rs 511, respectively.Larsen & Toubro has declined 4.5% to Rs 3,005, and BHEL is down 4% at Rs 2,009.Cipla has gaind 1.5% at Rs 221.Out of 2,598 stocks traded so far, 1,317 have advanced, 1,226 have declined and the rest are unchanged.