A House committee looking into the deadly 2012 attacks in Benghazi, Libya is interviewing former Defense Secretary Leon Panetta as the investigation shifts its focus from the State Department to the Defense Department and CIA.

The interview with Panetta follows a four-hour, closed-door session this week with former CIA Director David Petraeus.

Panetta has not testified before the Benghazi panel until now, but he told Congress in 2013 that time, distance and the lack of an adequate warning prevented a more immediate response to the September 2012 attacks that killed U.S. Ambassador Chris Stevens and three other Americans.

Panetta told MSNBC this week that "there was never any order to stand down. On the contrary, the whole effort was to do everything possible to try to save lives."