Erasing initial gains, the Sensex at the Bombay Stock Exchange was trading 185 points in the negative territory at 16,656 in late morning deals. The Sensex, which had gained 76 points in opening trade, fell by 80 points, or 0.48 per cent, to 16,760 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 52 points at 5,005.