The Federal Bureau of Investigation is investigating a cyber intrusion at the Democratic National Committee, amid concerns hackers working for Russia are attempting to use the breach to influence the US presidential election.
"A compromise of this nature is something we take very seriously, and the FBI will continue to investigate and hold accountable those who pose a threat in cyberspace," the FBI said in a statement on Monday.
Emails among DNC employees were released by anti-secrecy group WikiLeaks over the weekend appearing to expose favouritism for presumptive Democratic nominee Hillary Clinton over her chief rival in the primary contest, Senator Bernie Sanders.
The correspondence prompted the resignation of DNC chairwoman Debbie Wasserman Schultz on Sunday, effective at the end of the party's convention in Philadelphia. Protesters jeered Wasserman Schultz on Monday at a meeting ahead of the convention.
Separately, the US House of Representatives intelligence committee has been briefed on the hack and would seek information on any potential connection to Russia or another state, said Representative Adam Schiff, the senior Democrat on the panel.
Clinton campaign manager Robby Mook told CNN on Sunday that the emails were released by suspected Russian hackers in order to sow discord at the convention and help Republican nominee Donald Trump, her rival in the November 8 presidential election.
The Trump campaign dismissed the allegation as absurd.
