The fact that Harzi has been freed from detention "doesn't mean he's any less a suspect," the official said, adding Harzi does not appear on video taken of the Benghazi compound.

Investigators have identified at least 15 people who may be suspects, the official told CNN, indicating some were identified on the video.

"We will get indictments," the official said. "but it's not possible to put a timetable on it."

Reports on the attack

In December, an independent review of the Benghazi assault cited "systemic failures and leadership and management deficiencies" at the State Department.

Four State Department officials, including two who oversaw security decisions for Benghazi, were disciplined a day after the report was released.

Clinton got a copy of the report and said in letters to State Department chiefs that she accepted its recommendations to beef up security and intelligence gathering in high-threat areas.

Before the report came out, Clinton had popular approval ratings in nationwide polls.

A December Bloomberg National Poll showed 70 percent of Americans had a mostly favorable view of her. Polls from Politico/George Washington University, ABC News/Washington Post and the Siena College Research Institute also showed high marks.