A Chinese-American woman who worked for the Federal Bureau of Investigation (FBI) has been accused of spying for Beijing.
Ms Leung claims she is innocent
Katrina Leung has been charged with passing on classified nations security information to China, allegedly obtained from her lover and FBI "handler", James Smith.
Mr Smith has also been charged with gross negligence after allegedly allowing her access to secret documents during "debriefing" sessions at her home.
Correspondents say that the scandal could prove a great embarrassment to the FBI and the Republican party, with whom Ms Leung - a Los Angeles socialite - had close links.
Ms Leung was arrested on 9 April and charged with "obtaining a classified national security document for the purposes of aiding a foreign nation".
She has claimed that she is innocent, but has been denied bail.
Former Agent Smith not only betrayed the trust the FBI placed in him, he betrayed the American people he was sworn to protect.
Robert S Mueller, FBI Director
At the same time, Mr Smith, a former FBI special agent, was charged with gross negligence but given bail.
Authorities said that Ms Leung was recruited to work for the FBI in the 1980s and began an affair with Mr Smith.
According to the prosecution's affidavit, she was paid $1.7m over 20 years by the FBI, and operated under a number of aliases, including "parlormaid".
But during this time, the prosecution alleged, she was also working as a double agent for the Chinese government.
Prosecutors said that they found classified documents at Ms Leung's home, including a secret 1997 memorandum about Chinese fugitives.
Network of contacts
The affidavit also said that the FBI secretly searched her luggage when she left for a trip to China in November 2002 and found six photographs of former and current FBI agents.
When she returned from the trip, her luggage was covertly searched again, and the photos were no longer there.
It was alleged that Mr Smith came to Ms Leung's San Marino home, which she shares with her husband and son, for "debriefing sessions".
During the times of his visit, she was able to copy documents from his briefcase which she then passed on to Chinese agents.
Mr Smith was alerted to her duplicity by another FBI agent with whom she allegedly also had an affair, but he continued to see her.
A statement by the FBI Director, Robert S Mueller, said the day of the arrests was "a sad day for the FBI".
"Former Agent Smith not only betrayed the trust the FBI placed in him, he betrayed the American people he was sworn to protect.
"Allegations that he caused the loss of classified information, as well as his personal indiscretions with Ms Leung, are very serious and warrant a strong response," the statement said.
Ms Leung's lawyers, however, said that she is a "loyal American citizen".
"She repeatedly endangered herself in order to make significant contributions to the security and well-being of the United States.
"We believe that when the full story is known, Ms Leung will be cleared of all wrongdoing," the lawyers said.
Ms Leung was well-known in the Chinese-American community and also had a network of contacts in China.
In 1999 she organised a banquet for then Chinese premier Zhu Rongji when he visited the USA.
She also organised fundraising activities for the Republican party and accompanied a former Republican mayor on a trip to China in 1998.