A faltering monsoon making marginal progress after a late onset amid uncertainty about upcoming macro data - IIP for April and CPI for May tomorrow - also weighed.
Auto, banking, IT, power, refinery and capital goods stocks saw heavy selling.
Blue-chips like RIL, Tata Motors, ICICI Bank, SBI, HDFC Bank, Infosys, M&M, Axis Bank and TCS were trading lower.
The 30-share gauge resumed strong, in line with firm Asian cues, on the back of an overnight sharp rise on the Wall Street following optimism that the Greece may be close to a deal with creditors.
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The Sensex touched a high of 27,000.14, up 159.64 points, or 0.59 per cent, before slipping to 26,570.48 at 1132 hours, a loss of 270.02 points, or 1.01 per cent.
Yesterday, it had jumped 359.25 points, or 1.36 pct.
Similarly, the broader NSE Nifty moved in a range of 8,163.05 and 8,062.05 before trading at 8,036.80 at 1132 hours, a fall of 87.65 points, or 1.08 per cent.
Among Asian markets, Hong Kong, Japan, Singapore and South Korea turned higher while China and Taiwan moved down.