The scientist, Abraham Lesnik, of suburban Los Angeles, works in the development of anti-missile systems for aircraft and holds a Department of Defense security clearance of Secret, Special Access, according to his resume filed in court papers.
The FBI has conducted three separate searches of Lesnik's home in Valley Village, Calif., according to Lesnik's lawyer, Marc Harris.
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Investigators in the case say Lesnik's Boeing laptop computer has been turned over to the FBI after questions were raised as to whether classified data ended up in the hands of unauthorized individuals including foreigners.
Lesnik's lawyer says his client "has never improperly transmitted any classified information to anyone."
Lesnik's neighbors say FBI agents have been conducting a 24-hour surveillance of his home for the past few weeks.
An FBI spokesperson confirmed search warrants had been served but said the affidavits filed with the court were sealed, and no other information on the case could be made public.
Boeing spokesperson Walt Rice tells ABC News, "Boeing is cooperating with U.S. Government investigators in this case, and as such, we cannot comment further."