The Bombay Stock Exchange Sensex ended 259.48 points down to 32,014.19, and the National Stock Exchange Nifty dropped 78.85 points to 9,978.55 on Tuesday, after days of staying above the 10,000 mark. Analysts attributed the plunge in Indian shares to the market regulator asking stock exchanges to take action against 331 suspected shell companies.

Both indices had opened higher before immediately declining in morning trade. Sensex had opened 58 points higher because of heavy buying by domestic institutional investors, Mint reported. Tata Steel’s better-than-expected first quarter earnings, intense buying of shares of companies such as Hindustan Aluminium, Nalco and Vedanta, and a rise in auto, healthcare and IT stocks also contributed to the early gains.

Realty (-4.53%) and telecom (-18.36%) stocks on the BSE index plunged during trading in the afternoon. Dr Reddy’s Labs, Coal India, the State Bank of India and ITC were the worst performers on the Sensex. Tata Steel, Cipla and Bajaj Auto gained the most.

On the Nifty, Dr Reddy’s, Bharat Petroleum,Bharti Infratel and the Indian Oil Corporation were the biggest losers. Hindalco, Vedanta Limited and Cipla were the best performers.

Other Asian markets experienced a mixed day. Japan’s Nikkei declined 59.88 points to close at 19,996.01 points, and Taiwan’s TSEC 50 index also lost 10.41 points. However, the Hong Kong Hang Seng ended 164.55 points up, and the Shanghai SE Composite index closed flat.

The Indian rupee dropped 15 paise to 63.83 to the dollar.