Stock index futures extended losses on Thursday, following a steep drop in European equity markets and commodity prices as investors fretted about Europe's debt crisis.

S&P 500 futures fell 8.7 points and were below fair value, a formula that evaluates pricing by taking into account interest rates, dividends and time to expiration of the contract. Dow Jones industrial average futures were off 64 points, and Nasdaq 100 futures lost 10.75 points.

(Editing by Jeffrey Benkoe)