Organising committee spokeswoman Nancy Park said the defence ministry and a cybersecurity team were investigating the outage that occurred last night.
"It didn't affect the opening ceremony," Park said. "It went as planned. We just had some issue with our internal systems, but we are working to normalise that."
She said the systems were almost back to normal about 15 hours after the problems were discovered.
South Korea's Yonhap news agency reported that servers were shut down to prevent damage to technical systems, causing problems with the Pyeongchang Olympic website.
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"We don't want to speculate right now," she said. "It's not good to guess."
She said the outage affected only "non-core" systems and had no impact on "the actual events" during today's first full day of competition.
Organisers suggested technical problems might have been caused by the mountainous region in which the Olympics are based.
Security experts have cautioned that large events like the Olympics are targets for hacking, even in a country like South Korea, which produces some of the world's most sophisticated technology.