Systems problems are being blamed as the Chicago Board of Options Exchanges finally managed to open around 1 p.m. New York time Thursday.

The CBOE, the largest U.S. options exchange, said on its status page about 1:10 p.m. that systems were operating normally.

Chicago Board of Options Exchange spokeswoman Gail Osten says that the exchange failed to open at 9:30 a.m. New York time. Osten can't give a reason.

The Chicago Tribune reported that the delay meant investors could not trade CBOE's exclusive options on the S&P 500 Index and the CBOE volatility index. CBOE is run by CBOE Holdings Inc.

Trading continued on the other U.S. options exchanges.

Stock options give the holder the right, but not the obligation, to buy and sell stocks. Many of the most frequently-traded stock options are bought and sold on its exchange.

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