Index values for Dow, S&P 500 are working again after hourlong freeze

A trader signals an offer in the Standard & Poor’s 500 stock index futures pit at the CME Group in Chicago on Dec. 14, 2010.

Scott Olson | Getty Images News | Getty Images

The data feeds for key market averages had an issue on Thursday that caused the calculations for the S&P 500 and the Dow Jones Industrial Average to halt for about an hour. Trading continues normally and individual stock prices did not appear affected.

The CME Group confirmed to CNBC that there were issues affecting at least the calculations of those two indexes on Thursday for its customers. It appears the calculations for the Dow and S&P 500 froze at about 10:41 a.m. ET and then resumed shortly before noon.

Issues with data feeds for the indexes do not necessarily affect trading. Futures markets for the S&P 500 and the Dow appeared to be operating normally during the pause.

The SPDR S&P 500 ETF Trust (SPY), a common vehicle for investors to make broad market bets, also appeared to be actively trading.