At the stock markets, after a strong opening, the Sensex at the Bombay Stock Exchange soon surrendered all its initial gains, and had slumped 216 points, or 0.7 percent, to 31,384 a short while ago.The Nifty at the National Stock Exchange had dropped 67 points, to 9,804. And at the forex market, the rupee also quickly erased all its early gains, and had depreciated 20 paise, to 65.64 against the dollar in afternoon deals.