– The suspected hacking attempt on the Democratic National Committee's voter database this week was a false alarm and the unusual activity that raised concern was merely a test, party officials said Thursday.

The blunder was caused by a lack of communication between the national committee and one of its state branches, the officials said. The Michigan Democratic Party had hired hackers to simulate an attack known as phishing, but did not inform the national committee.

The Michigan Democratic Party's test had attributes similar to actual hacking, said Bob Lord, the national committee's chief security officer. When the Democratic National Committee was contacted by cybersecurity experts this week about the activity, it notified the FBI out of fears that it was another Russian attempt to penetrate the committee, as Moscow did during the 2016 presidential campaign.

The jolts of panic caused by what turned out to be an intraparty action underscored the fear of another major breach of the party's systems just weeks before the midterm elections, even as computer security has been prioritized and shored up since 2016. U.S. intelligence officials have said there continue to be real threats from Russia to interfere in U.S. elections.

"There are constant attempts to hack the DNC and our Democratic infrastructure, and while we are extremely relieved that this wasn't an attempted intrusion by a foreign adversary, this incident is further proof that we need to continue to be vigilant," Lord said.

Brandon Dillon, chairman of the Michigan Democratic Party, called the situation a "misstep" and said it was part of efforts to improve cybersecurity defenses "especially as the Trump administration refuses to crack down on foreign interference in our elections."

The hacking simulation was detected late Monday by cybersecurity firm Lookout, which informed the Democratic National Committee. A fake page appeared to be aimed at hacking the Democratic National Committee's VoteBuilder database, which Lord has referred to as "the party's most sensitive information."