Shares of healthcare companies Monday witnessed massive sell-offs, led by Sun Pharmaceutical Industries that plummeted over 9 per cent amid reports that a lawsuit has been filed against generic companies in the US.

Sun Pharma shares dived 9.39 per cent to close at Rs 396.85 on the BSE. During the day, the scrip plunged 20 per cent to Rs 350.40 -- its 52-week low.

It was the biggest drag on the BSE key index at close of trade.

On the NSE, shares tumbled 9 per cent to close at Rs 398.10.

Among others, shares of Cadila Healthcare Ltd plunged 7.18 per cent, Sun Pharma Advanced Research Company 6.37 per cent, Wockhardt Ltd 5.57 per cent, Lupin Ltd 4.24 per cent and Glenmark Pharmaceuticals Ltd 4.20 per cent on the BSE.

Led by the sharp fall in these scrips, the BSE Healthcare index closed at 13,310.47, down 486.83 points or 3.53 per cent.

According to media reports, a lawsuit has been filed against Teva Pharmaceuticals and 19 other generic companies in the US.

The lawsuit named Taro Pharmaceuticals USA, the US-based subsidiary of Sun Pharma, reports added.