The Democratic National Committee said Wednesday that it had discovered an attempt to steal credentials to gain access to its voter database.

An unidentified person or group created a login page in an attempt to trick DNC staffers into giving up their usernames and passwords, a strategy known as a phishing attack. The attempted breach, which was unsuccessful, was first reported by CNN.

Later on Wednesday, the DNC clarified that upon further investigation the attempt appeared to have been an "unauthorized" test by an unnamed third party.

The DNC and the Democratic Congressional Campaign Committee were victims of a similar attack in 2016, leading to the high-profile release of Democratic emails during that year’s presidential race. Twelve Russian intelligence officers have been indicted in connection with that breach.

Bob Lord, chief security officer for the DNC, confirmed that it had detected the latest attempted breach.

“This attempt is further proof that there are constant threats as we head into midterm elections and we must remain vigilant in order to prevent future attacks," Lord said in an email. "While it’s clear that the actors were going after the party’s most sensitive information — the voter file — the DNC was able to prevent a hack by working with the cyber ecosystem to identify it and take steps to stop it."

The attempt was the latest in a string of reports of cyberattacks aimed at U.S. politicians, seeking to break into their networks and gather information ahead of this year’s midterm elections.

U.S. intelligence officials have raised alarms about the danger, warning of a repeat of attacks that were prominent in 2016.

"The warning lights are blinking red again," Dan Coats, the director of national intelligence, said last month.

In the most recent case, the DNC was alerted by a cloud service provider and a security research firm of the existence of a fake login page designed to look like one party workers use to access the third-party vendor that houses the DNC voter file.

The FBI did not immediately respond to a request for comment Wednesday.

Other reported hacking attempts this year targeted conservative nonprofit organizations, a Democratic senator and two Democratic House candidates in California.

Clint Watts, a former FBI special agent and MSNBC contributor who has testified before Congress, said the U.S. remains unprepared.

"Why does this hacking & influence continue targeting US? Because the US government response is weak & disjointed, adversaries using cyberspace and social media platforms as battlefields against America," Watts said on Twitter.

This story is developing.