Federal Bureau of Investigation agents are investigating the hacking of the Democratic National Committee's emails after thousands of messages were posted last week to WikiLeaks, officials said Monday.
"The FBI is investigating a cyber intrusion involving the DNC and are working to determine the nature and scope of the matter," officials said in a statement. "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."
WikiLeaks on Friday released more than 19,000 emails and over 8,000 attachments from seven key figures in the Democratic National Committee. The emails were sent between January 2015 and May 25, 2016, according to WikiLeaks.
The emails suggested that the DNC was favoring former Secretary of State Hillary Clinton over her rival, Sen. Bernie Sanders, during the primary season, prompting Clinton's campaign to point to a massive hacking of DNC computers in June that cybersecurity firms linked to the Russian government.
Donald Trump on Monday dismissed as a "joke" claims by Clinton's campaign that Russia is trying to help Trump by leaking the emails.
Rep. Debbie Wasserman Schultz, head of the DNC, announced she would step down after the Democratic National Convention concludes, apparently as a result of the email leak.
The leaked emails are from communications director Luis Miranda, national finance director Jordon Kaplan, finance chief of staff Scott Comer, finanace director of data and strategic initiatives Daniel Parrish, finance director Allen Zachary, senior advisor Andrew Wright and Northern California finance director Robert (Erik) Stowe, according to WikiLeaks.
The Associated Press contributed to this report.