(Reuters) - The Chicago Board Options Exchange delayed its opening on Thursday due to "downloading" issues, preventing investors from accessing its exclusive options on the Standard & Poor's 500 Index and the CBOE Volatility Index.
Trading continued on the 10 other U.S. options exchanges.
At least two of CBOE's competitors invoked "self-help" against CBOE, an action taken when another exchange is having system problems.
The Chicago exchange, run by CBOE Holdings Inc
"Some users are experiencing issues downloading CBOE and CFE products this morning. The CBOE is looking into this issue and will advise," the CBOE said on its website before its regular opening time of 9:15 am local time. CFE is CBOE's futures market.
Later CBOE said systems for all its exchanges except its floor-based Chicago options exchange were functioning normally.
"The CBOE has not yet determined an open time for C1," the exchange said on its website, referring to its main exchange, based in Chicago. CBOE will advise when a start time is determined."
At least one trader was unruffled.
"There is no shortage of other venues to trade on," said Steve Sosnick, equity risk manager at Timber Hill, a division of Interactive Brokers Group. "We have not heard much about the cause of the outage at CBOE."
The SEC is "monitoring the situation" a spokesman said.
(Reporting by Doris Frankel, Ann Saphir and Sarah N. Lynch; Editing by Alden Bentley and Andrew Hay)