In the previous trading session, the frontline index S&P BSE Sensex ended the day with minor gains of 0.06 per cent. However, in the pre-opening session today, the index opened in red, down by 0.51 per cent to the level of 55,419.83 and by 9.15 am, it fell to 54,928.29, which was a decline of 1.39 per cent.