Giving up all its initial gains, the Sensex at the Bombay Stock Exchange fell 40 points, or 0.2 percent, to 19,693 in afternoon trade, a short while ago. But earlier in the morning, the Sensex had surged 293 points, or 1.5 per cent, to 20,026, after capital market regulator, SEBI allowed overseas entities to invest in government securities without any auction mechanism. Stock markets in Hong Kong, Taiwan, Singapore, South Korea and Indonesia had gained between 1 percent, and 1.8 percent.