The auction of NTPC shares saw good response from investors in the initial hours of sale today with bids coming in for over 30.51 crore shares in the first three hours of trade.The government is offloading 78.32 crore shares or 9.5 per cent stake in the state-owned power major NTPC and has fixed a floor price of Rs 145 a share.The stake sale would fetch over Rs 11,300 crore to the exchequer, making it the biggest disinvestment so far this fiscal.On the BSE, shares of NTPC opened on a weak note and fell by 2.01 per cent in the opening trade to Rs 149 apiece.The one-day auction began this morning at 0915 hrs on the stock exchanges and had attracted bids for 30.51 crore shares by 1215 hrs against an offer of 78.32 crore shares.