The Sensex is now down 521 points at 18,142.The NSE Nifty is down 161 points at 5,322.Satyam and Infosys have tumbled nearly 7% each to Rs 408 and Rs 1,503, respectively. TCS and Wipro have slumped around 5.5% each to Rs 899 and Rs 429, respectively.Hindalco has dropped nearly 5% to Rs 173. ONGC and Maruti have shed 4.4% each at Rs 1,027 and Rs 835, respectively.Bharti Airtel has slipped nearly 4% to Rs 900. ICICI Bank and Grasim have declined over 3% each to Rs 1,151 and Rs 2,886, respectively.Out of 2,790 stocks traded so far, 1,486 have declined, 1,258 have advanced and 46 are unchanged.