Panic selling by FIIs saw the BSE Sensex tumbling 506 points, or 3.2 per cent, to close at 15,066 levels on Monday. During the early trade, it plunged more than 700 points, breaking the 15,000 mark before paring some of the losses. The 50-share Nifty ended in the red losing 2.7 per cent to close at 4500 levels. Earlier in the day, it had stooped to new lows to hit the year-to-date’s low seen in January 22, of 4434 levels.