The Department of Justice's government watchdog has released a report faulting the Federal Bureau of Investigation for how it has handled information on potential homegrown terror threats.

The report, released Wednesday by Inspector General Michael Horowitz, focused on the bureau's efforts to investigate and identify homegrown violent extremists, or HVEs, which it defined as "global jihad-inspired individuals who are in the United States, have been radicalized primarily in the United States, and are not receiving individualized direction from a foreign terrorist organization (FTO)."

Among the problems that the investigation found were that some of those designated extremists went on to conduct terror attacks after they had already been on the FBI's radar.

"Since September 11, 2001, HVEs have carried out over 20 attacks in the United States, some of which occurred after the FBI closed a counterterrorism assessment or investigation on the individual," the report explained. "During our audit, we found at least six attacks committed in the United States by individuals who the FBI had previously assessed or investigated and who were subsequently categorized as HVEs."

Among such attacks listed in the inspector general's report are the 2013 Boston Marathon Bombing, the 2009 Fort Hood Massacre, and the 2016 Pulse Nightclub shooting.

Furthermore, while the bureau conducted reviews in the wake of attacks by people previously designated as HVEs in order to figure out what went wrong in the investigation process, a related news release explained, "FBI did not ensure that all field offices and headquarters implemented recommended improvements and subsequent policy requirements."

Therefore, it added, "FBI field offices continued to conduct some counterterrorism assessments that did not meet FBI requirements or standards."

But the report also noted other follow-through problems associated with a widespread review of previously closed counterterrorism assessments that the FBI conducted in 2017. The review found that 6% of the cases it looked over didn't properly assess potential threats and needed further investigation, the reports notes.

However, "nearly 40 percent" of those flagged assessments "went unaddressed for 18 months after deficiencies were known," the report said. "As a result, potential terrorist threats were not mitigated for more than 1 year."

In a Wednesday video address describing the investigation's findings, Horowitz acknowledged, "This is a particularly challenging area for the FBI because of the need to preserve constitutional protections while maintaining national security."

He added that his office has made seven recommendations for the FBI to address the listed problems, "and the FBI has agreed with all of them."

Horowitz was also the inspector general behind the December report on the origins of the FBI's Trump-Russia probe that found "at least 17 significant errors or omissions in the Carter Page FISA applications."