The Sensex opened with a negative gap of 445 points at 13,086, and soon touched a low of 13,052.
The index has recovered partially and is now down 277 points at 13,254.
Ranbaxy has slumped 5.7% to Rs 396. Bharti Airtel and Reliance Infrastructure have plunged around 4.5% each to Rs 730 and Rs 803, respectively.
DLF, Satyam, ICICI Bank and Jaiprakash Associates have dropped over 4% each to Rs 414, Rs 353, Rs 602 and Rs 141, respectively.
HDFC has shed 3.5% at Rs 2,127. BHEL has slipped 3% to Rs 1,580.
