Erasing all its initial gains, the Sensex at the Bombay Stock Exchange stood a marginal 11 points in negative territory, at 19,773 in afternoon deals, a short while ago. But earlier in the morning, the Sensex had opened with a gain of 69 points, or 0.4 per cent, at 19,853, on sustained buying by funds and retail investors, amid firm Asian markets.The 30-share Sensex had climbed nearly 360 points in the previous four trading sessions.