The malfunction that kept the Chicago Board Options Exchange shut for more than three hours Thursday morning did not stem from any outside intervention in its systems, the exchange's parent CBOE Holdings Inc said.
"The malfunction that impacted CBOE was an internal systems issue and not the result of any outside influence," CBOE said in a statement. An executive had earlier said the incident was not related to any computer hacking.
Trading in some options at CBOE opened at 12:50 ET, more than three hours after the exchange's usual start time.
"The issue, which affected validation of certain orders and the communication of cancel/fill reports, has been corrected," CBOE said.
(Reporting by Ann Saphir; Editing by Chizu Nomiyama)