Erasing initial gains, the Sensex at the Bombay Stock Exchange was trading 37 points in the negative territory at 20,693 in afternoon trade, a short while ago. The 30-share index had opened 42 points in the green. Snapping a five-day losing streak, it had ended with a gain of 36 points yesterday.The Nifty at the National Stock Exchange was trading 15 points in the red at 6,160.