Chinese authorities killed or imprisoned 18 to 20 CIA informants in China in the period of 2010-2012. This was reported by The New York Times referring to the sources among current and former American officials.
As the agency informed, Beijing managed to cripple American surveillance network that had taken years to build.
Officials noted that the intelligence breach was "one of the worst in decades".
The investigators have not found the cause of the occurrence yet.
"Some were convinced that a mole within the C.I.A. had betrayed the United States. Others believed that the Chinese had hacked the covert system the C.I.A. used to communicate with its foreign sources. Years later, that debate remains unresolved," the message says.
CIA refused to comment on the information.