After opening 51 points higher, at 18,520, this morning, on bargain-hunting by investors, the Sensex at the Bombay Stock Exchange climbed further and at one stage had gained almost 100 points. But the market later gave up all its initial gains, and the Sensex had slipped as much as 229 points or 1.2 percent into negative territory, at 18,240, amid high volatility, in afternoon deals, a short while ago. The 30-share index has already lost more than 1,100 points in the last eight trading sessions.Elsewhere in Asia, stock markets in China, Hong Kong, Indonesia and Singapore were trading mixed, today. In the US, the Dow Jones Industrial Average had declined 0.7 percent, overnight.