Updated

The former CIA officer arrested Monday for unlawfully retaining classified information may have helped China execute or imprison several U.S. informants, according to The Wall Street Journal, citing U.S. officials familiar with the matter.

Jerry Chun Shing Lee, 53, unlawfully possessed top secret information whose disclosure could cause “exceptionally grave damage to the National Security of the United States,” the FBI wrote in the affidavit supporting his arrest.

Lee, whose security clearance was terminated when he left the CIA in 2007, improperly retained books containing “true names and phone numbers of assets and covert CIA employees,” the affidavit read.

The New York Times was the first to report that U.S. officials believe that Lee may have played a key role in outing US informants working in China, who started to go dark in 2010.

One of those officials was shot to death in front of coworkers in the courtyard of a Chinese government building, as a clear warning to other potential traitors, according to sources cited by The Times.

The paper cited sources who said Lee, who began working for the CIA in 1994, left because he was unhappy at his career progression there.

Between 18 and 20 key CIA sources in China were systematically jailed or killed from 2010 to 2012, in what US officials described as one of the worst intelligence failures in decades, according to the Times.

The losses were reportedly reminiscent of the significant damage caused by rogue agents Aldrich Ames and Robert Hanssen, who became Russian spies.

The FBI said that its inquiry, which began in 2012, involved luring Lee back to the U.S. and searching his hotel rooms in Hawaii and Virginia.

As evidence mounted, the FBI interviewed Lee several times in 2013.

Lee never mentioned possessing classified information during those interviews, according to the arrest affidavit.

It is unclear whether Lee will be charged in the informants' deaths.