The investigation led by the US Justice Department’s inspector general deals with allegations against FBI officers in six cities, The Wall Street Journal said on Thursday.
"Upon learning of these allegations of misconduct, action was taken to reassign certain personnel to non-operational roles while the allegations are reviewed," FBI said in a comment to the newspaper.
The FBI, however, refused to provide the information about specific suspicions.
"All FBI employees are held to the highest standards of conduct, and allegations against any employee are taken very seriously," the FBI said in a statement.
The Federal Bureau of Investigation has about 35,000 personnel, with a large presence of special agents and support staff in embassies across the world.