The hacker calling themselves "Guccifer 2.0" is claiming credit for the Friday night release of personal cell phone numbers and private email addresses of Democratic House members.
The data -- posted to their WordPress blog -- also contains the contact information for staff members and campaign aides.
In the trove of information released on Friday "Guccifer 2.0" also uploaded files to the blog post that contains login information to subscription services used by the Democratic Congressional Campaign Committee, including Lexis-Nexis and Washington newspapers.
In a statement, DCCC Press Secretary Meredith Kelly said: "As previously noted, the DCCC has been the target of a cybersecurity incident, and we are cooperating with federal law enforcement in their ongoing investigation. We are aware of reports that documents claimed to be from our network have been released and are investigating their authenticity."
Nancy Pelosi: DNC hack is 'electronic Watergate'
The hacker also uploaded documents analyzing candidates for Florida's 18th congressional district, and a fundraiser memo to House Minority Leader Nancy Pelosi about Morgan Carroll's congressional campaign in Colorado.
The hacker wrote in the blog post, "It's time for new revelations now. All of you may have heard about the DCCC hack. As you see I wasn't wasting my time! It was even easier than in the case of the DNC breach."
The person claiming to be Guccifer 2.0 earlier posted several documents on the Internet and sent them to media outlets including Gawker, portraying the documents as coming from the hack of the Democratic National Committee's files. The documents included a file about Republican nominee Donald Trump and what looked like memos about DNC operations. But the claims made by the "Guccifer 2.0" individual were viewed with a dose of skepticism by experts who have analyzed the events.
There is no way to verify the identity of the individual known as Guccifer 2.0. The name is a reference to a Romanian hacker who pleaded guilty to hacking several prominent politicians and figures, including former Presidents George W. Bush and George H.W. Bush, who went online by Guccifer.
So far the administration has not publicly identified who it believes may be behind the hack. However, intelligence and law enforcement officials have told CNN Russia is the most likely suspect.
In July, WikiLeaks founder Julian Assange said he believed his group's release of hacked Democratic National Committee emails affected the 2016 election, adding the group is holding unreleased information about Hillary Clinton's presidential campaign.
"We have more material related to the Hillary Clinton campaign," Assange told CNN's Anderson Cooper on "Anderson 360" on July 29. "That is correct to say that."
On Thursday, Pelosi called reports that the hack of the DNC was even broader than had been made public, labeling it an "electronic Watergate."
"Let me just say this in terms of the presidential campaign: This is an electronic Watergate," Pelosi said. "This is a break-in."
A US official this week confirmed a reports, first in the New York Times, that the hack of the DNC was broader than had previously been known.