Washington

The head of counterintelligence at Lawrence Livermore National Laboratory in California has resigned following revelations that he had a sporadic, 15-year affair with an alleged Chinese spy.

William Cleveland, a former special agent with the Federal Bureau of Investigation (FBI), resigned from his position at the nuclear-weapons laboratory on 10 April, after ten years in charge of its counterintelligence office. His resignation preceded press revelations that an official matching Cleveland's description had a relationship with Katrina Leung, a prominent Chinese-American community leader and Republican Party fundraiser. Leung worked for the FBI but is now accused of working as a double agent for China. She was arrested on 9 April and is in prison awaiting trial. Cleveland has not been charged with any offence and is cooperating with the authorities.

“The allegations in the affidavit are personal in nature, and there is absolutely nothing in it to indicate that security was compromised at Livermore,” Susan Houghton, a spokeswoman for the laboratory, told Nature. Without naming Cleveland, Houghton added that the lab has barred the official in question from the campus and impounded his personal equipment pending an investigation. Congressional leaders were briefed on the case last week, but the committees responsible for overseeing the lab have yet to decide whether they will conduct their own investigation.

The main allegations against Leung involve her relationship with FBI agent James Smith, who handled her work for the bureau. It is not clear how much, if any, information allegedly passed by Leung to China involved the Livermore laboratory. But she seems to have some knowledge of the investigation of a scientist there, Peter Lee, who confessed in 1997 to leaking nuclear-weapon and submarine secrets to China. According to the FBI affidavit, a search of Leung's residence in December 2002 turned up a list of telephone numbers for 'Royal Tourist', the codename for the FBI's investigation into Lee.

Cleveland was said to be well respected at the lab, where he trained researchers and managers on how foreign agents might try to befriend them to gain classified secrets. He was also responsible for debriefing scientists who had travelled to sensitive countries or recently hosted foreign visitors. “He was a superstar of counterintelligence at the Department of Energy,” says Peter Stockton, who served as a security consultant to former energy secretary Bill Richardson, and now works with the Washington-based Project on Government Oversight.

The latest espionage case could carry adverse consequences for the laboratory or its contractor, the University of California, which is already under fire for its management of Los Alamos National Laboratory in New Mexico (see Nature 421, 99; 200310.1038/421099a), and for an earlier, inconclusive spying probe involving Wen Ho Lee, a researcher at Los Alamos.