The Sensex opened with a negative gap of 292 points at 15,684, and soon tumbled to a low of 15,492. The index is now down 365 points at 15,610.The NSE Nifty is down 84 points at 4,687.Larsen & Toubro (L&T) has plunged over 9% to Rs 2,715.BHEL has slumped 6.4% to Rs 1,897. Reliance Energy has dropped 4.7% to Rs 1,210.ICICI Bank and HDFC Bank have shed around 3.5% each to Rs 860 and Rs 1,242, respectively.Reliance Communications has slipped 3% to Rs 527. Grasim and Maruti are down 2% each at Rs 2,725 and Rs 915, respectively.ONGC, however, has moved up over 1% to Rs 966.