A former CIA officer has been arrested in the US on charges of unlawful retention of classified information.
Jerry Chun Shing Lee, a naturalised US citizen, was held at New York's JFK airport on Monday, the US justice department said.
He worked for the CIA between 1994 and 2007, when he left for Hong Kong.
The case is thought to be linked to an FBI investigation which began in 2012, into the crippling of the CIA's spy operation in China.
In the two years prior, some 20 informants had been killed or jailed - one of the most disastrous failures of US intelligence in recent years.
But officials did not know whether to blame a mole or data hack.
When Mr Lee left the CIA in 2007, "those who knew him said he left the agency disgruntled after his career plateaued", reported the New York Times.
Mr Lee remained in Hong Kong and only returned to America in 2012 - according to one report, lured by a fake job offer.
At that time, the US justice department said in a statement, FBI agents searched his hotel rooms in Hawaii and Virginia and found two small books with secret records.
They contained handwritten notes on details such as "true names and phone numbers of assets and covert CIA employees".
Mr Lee left the US in 2013, however, and has only now been detained while on another visit.
The statement says that Mr Lee, 53, has been charged "with unlawful retention of national defence information and faces a maximum penalty of 10 years in prison, if convicted".
Mr Lee, also known as Zhen Cheng Li, began his CIA career as a case officer, maintained a top secret clearance and signed non-disclosure agreements.
He has made no public comments on the issue, reports BBC.