The report issued Wednesday by the department's inspector general concluded that a dozen individuals who were under investigation and should have been on the list instead may have been able to enter and leave the United States.
CBS News said the report found that the FBI was frequently late in adding names to the list, and sometimes never added them at all. In addition, in 8 percent of the 216 investigations that were reviewed, the bureau failed to remove names of people who had been cleared.
"The FBI needs to ensure that it makes timely nominations to the terrorist watch list," said Inspector General Glenn Fine. "Failure to do so can have significant consequences for public safety."
FBI Assistant Director John Miller did not dispute the findings and said the FBI was implementing the recommendations made in Fine's report, CBS reported.