The group, known as Lulz Security, tweeted 'Tango down - CIA.gov,' and there were difficulties throughout the early evening accessing the agency's website.
The computer mischief appeared to be targeting the CIA's public website, which does not include classified data and has no impact on the CIA's operation.
CIA spokesman Marie Harf said the agency is looking into the reports.
It is sometimes difficult to tell if a website has been hacked, or if the claim alone drove so many people to the site that it crashed.
Efforts to access the website were met with an error message long after the breach began, around 6pm EST.
On Monday, the group accessed a Senate server that supports the chamber's public website but did not breach other files, according to a Capitol Hill law enforcement official.
The hackers said the release was a 'just for kicks' attempt to help the government 'fix their issues.' Read More