On Monday, the domestic benchmark indices wiped out the day's gains to end flat with a negative bias. Snapping its bull-run, Sensex erased around 500 points from its day's high to close at 51,329.08 levels, down by 0.04 per cent or 19.69 points. During the last half hour of the trading session, Nifty slipped in red to settle at 15,109.30 levels, down by 0.04 per cent or mere 6.50 points from its previous close.