The Sensex opened with a negative gap of 94 points at 18,920, and continued to drift deeper into red. The index is now down 669 points at 18,344.DLF has slumped almost 6% to Rs 947. Mahindra & Mahindra, HDFC Bank and ITC have plunged 5.5% each to Rs 688, Rs 1,490 and Rs 201, respectively.Reliance Communications has tumbled 5.3% to Rs 665. Larsen & Toubro has slipped nearly 5% to Rs 3,741.Cipla has shed 4% at Rs 194. Tata Motors and Satyam have dropped 3.7% each to Rs 685 and Rs 359, respectively.NTPC, Tata Steel and Reliance are down around 3% each at Rs 232, Rs 759 and Rs 2,718, respectively.Ranbaxy, however, has moved up nearly 1% to Rs 390.