A suspicious package shut down administrative offices at the Air Force academy for two hours on Thursday before workers were allowed to return.
The package was found in Harmon Hall just after 2 p.m., driving an evacuation and a large security response. There was no immediate word on what was found inside the package or why it prompted concern.
The area was roped off, and security forces, firefighters and security experts from the 10th Air Base Wing's engineering squadron were working inside Harmon Hall to determine what threat, if any existed.
The incident comes as the academy hosts students from 50 colleges and dozens of speakers for its annual National Character and Leadership Symposium, which continued without interruption.
Activities from the headquarters building were transferred to a command post on the 18,000-acre base, and activities elsewhere, including at Air Academy High School, continued.
Harmon Hall houses offices for superintendent Lt. Gen. Michelle Johnson and other administrative functions. It has no classrooms.
Academy spokesman John Van Winkle said the incident was similar to drills held regularly at the academy.
"We're going to err on the side of caution every time," he said.