(CNN) Update: The Democratic National Committee said late Wednesday that what it had earlier feared was the beginning of a sophisticated attempt to hack into its voter database, was, in fact, an unauthorized "simulated phishing test." Read the updated story here.

The Democratic National Committee contacted the FBI on Tuesday after it detected what it believes was the beginning of a sophisticated attempt to hack into its voter database, a Democratic source tells CNN.

The DNC was alerted in the early hours of Tuesday morning by a cloud service provider and a security research firm that a fake login page had been created in an attempt to gather usernames and passwords that would allow access to the party's database, the source said.

The DNC and the two companies involved in detecting the operation say they believe they thwarted a potential attack.

The fraudulent page was designed to look like the access page Democratic Party officials and campaigns across the country use to log into a service called Votebuilder, which hosts the database, the source said, adding the DNC believed it was designed to trick people into handing over their login details.

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