The online encyclopedia began to experience problems about 9:30 EDT as an error message on the site's front page stated its "servers are currently experiencing a technical problem," CNET reported.
The site loaded slowly and pages were only partially loading, visitors reported, with much of the site's content styles and layout missing.
In an e-mailed statement to CNET, Wikipedia said the outage was "due to networking issues with servers in Tampa, Fla."
Later in the day, Wikipedia blamed the outage on "a fiber optic cable cut near our Florida data center."
Wikimedia Foundation spokesman Jay Walsh said the organization was investigating the outage but felt there is "no reason to believe that it was intentional."