Erasing initial gains, the Sensex at the Bombay Stock Exchange was trading 275 points in the negative territory at 16,566 points when reports last came in. The Sensex, which had gained 76 points in opening trade, first fell by 80 points, or 0.48 per cent, to 16,760 and then further declined, after stocks of technology, banking, auto and capital goods companies succumbed to profit-booking. In a similar fashion, the broad-based National Stock Exchange Nifty index was down by 87 points at 4,970.