According to an investigation by The New York Times, the government of the PRC was able to either kill or imprison 18 to 20 CIA sources from 2010 to 2012; an article in Foreign Policy cited a higher number, putting the number of sources killed at at least 30.[9][10] A joint CIA and FBI counterintelligence operation set up to investigate the intelligence failure advanced three different theories[10][11] as to why the spy network was dismantled: (1) there was a mole within the CIA, (2) "sloppy tradecraft" and (3) PRC intelligence agents had hacked the covert system the CIA used to communicate with its foreign sources. The New York Times said that the debate over the cause remained unsolved while the a former American intelligence official cited by Foreign Policy said investigators concluded that it was caused by a "confluence and combination of events."[9] In January 2018, a former CIA officer named Jerry Chun Shing Lee was arrested and would eventually plead guilty[12][13] on suspicion of helping dismantle the network[11] while the Foreign Policy article ascribed, notwithstanding the arrest, the failure to the ability of the PRC intelligence agencies to penetrate the CIA's communication system.[9]