"I am not aware of any others that could be involved in this issue at the present time," Defense Secretary Leon Panetta told reporters.
"Obviously, as this matter continues to be investigated both on Capital Hill and by the inspector general, I'm sure that we'll have to wait and see what additional factors are brought to our attention."
The FBI investigation was triggered by Frederick Humphries, a veteran agent for the Tampa FBI field office, who is a friend of Kelley, said Lawrence Berger, general counsel for the Federal Law Enforcement Officers Association.
Kelley, who was a volunteer at MacDill Air Force Base in Florida, contacted Humphries about anonymous emails that questioned her character, a U.S. official and a source close to Kelley said.
Humphries took the information in the emails to the "appropriate components," Berger said. "He reported it to the proper channels and had no further part in the case."
Humphries is now the subject of an FBI investigation into whether he followed proper procedures in speaking to members of Congress about his concerns about how the FBI was handling Kelley's case.