Marketmen said higher industrial output numbers for January, which may ease the pressure on the Reserve Bank to cut interest rates to spur growth, also dampened investor sentiment to some extent.
After a firm start at 19,697.84, the Sensex tumbled by 140.46 points to 19,505.75 at 1330 hrs, with fall in bluechip stocks of banking and information technologies sectors.
Similarly, the broad-based National Stock Exchange index Nifty dropped by 48.70 points to 5,893.65, after touching a high of 5,952 at the outset.
They said a weak trend in the Asian region and lower opening in Europe after Fitch rating downgrade Italy and China's retail sales and industrial output missed market expectations.
Major losers were Infosys, Tata Consultancy Services, BHEL, State Bank of India, ICICI Bank, HDFC Bank, HDFC Ltd, Axis Bank and Hindalco.