The Chinese government systematically dismantled U.S. spying operations in the country since 2010 in the worst intelligence breach in decades, the New York Times reported on Saturday.
Current and former U.S. officials told the newspaper that China killed or imprisoned 18 to 20 of of the Central Intelligence Agency’s sources from 2010 to 2012.
The breach predated a 2015 hacking that gave Beijing access to thousands of government personnel records, including intelligence contractors.
The number of U.S. lost in China rivaled those lost in the Soviet Union and Russia during the betrayals of both Aldrich Ames and Robert Hanssen, who for years leaked details of U.S. intelligence to Moscow, the Times reported.
The CIA declined to comment to the Times report on Saturday.
The problem began to emerge in 2010, when the U.S. intelligence agency began receiving high quality information about the Chinese government from sources deep inside the government. But by the end of the year, the information began to dry up and in early 2011 the sources began disappearing.
These resources in China are regarded as precious assets by the CIA, as the extensive security apparatus in the country makes it exceptionally hard for Western spy services to develop sources there, the report said.
One of the sources was shot and killed in front of a government building as a message to others who might have been working with Washington, three officials told the Times, saying that was designed.
The breach was considered particularly damaging, but investigators still remain divided over the cause of the breach. Some investigators believed the Chinese had hacked the CIA's covert communications system. Others were convinced that there was a spy within the CIA, the newspaper reported.
The FBI and CIA opened a joint investigation based out of northern Virginia. The investigation ultimately centered on a former CIA operative who worked in a division overseeing China, but there was not enough evidence to arrest him.
China has recently stepped up its spying practices. Last year an FBI employee pleaded guilty to passing sensitive technology information to the Chinese government in return for money, hotels and prostitutes, according to the Times.
By 2013, U.S. intelligence concluded China's ability to identify its agents had been blunted, but the damage had been done. The CIA has tried to rebuild its network of spies in China since, officials told the newspaper.