Report reveals China's crackdown on CIA operations
Several had also been arrested and imprisoned. The revelations were made by former high-ranking officials of the US. Officials said that at least 18-20 CIA operatives were killed or arrested.
Authorities remained divided on how the Chinese could have found out about the operatives.
How China crippled the CIA's efforts
How did the killings begin?
In 2010, the US intelligence network within China was at its operational best.
However, by the end of 2010, analysts noticed that the flow of information was drying up and that several CIA sources were disappearing inside China.
By 2011-12, CIA operatives began disappearing more regularly. Most of them were Chinese officials who were recruited as they were disillusioned with their government's policies.
Assessing the damage
Sources said that in all, 18-20 operatives were identified who were either killed or arrested.
The number of operatives that were exposed rivalled that during the cold war.
Sources added that in one case, Chinese authorities shot an alleged CIA operative in front of his friends and colleagues to set an example.
The revelations also show the success and advancement of Chinese counter-intelligence.
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Investigators have no clue
The CIA and FBI began investigations into the disappearances of CIA assets.
While several officers believed that the Chinese may have hacked US communications, others were sure that there was a mole in the CIA who divulged the information.
Others in the FBI also believed that the agents were caught because they became too sloppy in their operations and gave themselves away.
Were US officials bugged?
FBI sources added that US operatives would frequent the same restaurants for meetings, and that the Chinese intelligence had bugged the restaurant and also placed operatives there as waiters to gather information about the US spies.
Spy disappearances suddenly stop
By 2013, the disappearances of CIA assets in China abruptly stopped. It was unclear why or how, but FBI and CIA authorities were relieved.
Investigators are still unable to ascertain how the Chinese managed to get the information and investigations are still underway.
Sources said the CIA is now trying to rebuild its network within China.
China is spying in the US
The US has in the past, arrested several US citizens accused of acting as spies for China.
These include a former FBI employee who pleaded guilty last year to passing on technology information to China for years, in exchange for money and prostitutes.
In another case, a longtime State Department employee was arrested for receiving cash payments from China and other luxury gifts.