YOKOTA AIR BASE, Japan — Base officials are investigating exercise procedures after two bomb threats, intended as part of an operational readiness exercise last week, were thought to be real.

“The investigation is ongoing as to the cause of the confusion,” said 2nd Lt. Thomas Wenz, a base spokesman.

The bomb threats were called in separately Thursday to the Officer’s Club and the Westside Chapel, Wenz said.

The threats were part of an exercise scenario to see how the staff in each building would respond, Wenz said. But because the wing inspector general’s office — the overall exercise organizers — weren’t informed of the plan, “they treated it as if they were real bomb threats.”

The buildings were evacuated, the area was cordoned off and canine units were brought in, Wenz said.

“There was no actual threat of a bomb,” Wenz said. “It was an exercise, but it hadn’t been coordinated.”

Emergency responders took prudent measures to “ensure the safety of Yokota and the local communities,” he said.

Wenz wouldn’t say which organizations were responsible for the unplanned “bomb threats,” just that each incident is under investigation.

He noted that everyone at Yokota and in the Air Force keeps a bomb-threat aid checklist next to the phone, instructing what to do in the event a bomb threat is received.

“The people who received the call followed the proper procedures and notified first responders,” he said. “You always assume that it’s real unless you know it’s an exercise scenario.”