Lockdown lifted at Arizona Air Force base after reports of shots fired

FILE - In this May 21, 2015 file photo a field of F-4 Phantoms are stored at the 309th Aerospace Maintenance and Regeneration Group boneyard in Tucson, Ariz. The last of thousands of F-4 Phantom jets that have been a workhorse for the U.S. military over five decades are being put to pasture to serve as ground targets for strikes by newer aircraft. (AP Photo/Matt York,File) (The Associated Press)

A lockdown at an Air Force base in Arizona was lifted Monday, more than an hour after "unconfirmed" reports of shots fired there, as a Pentagon official told Fox News it likely was a false alarm.

Davis-Monthan Air Force Base officials had urged everyone to seek shelter as on-site security investigated.

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Two airmen on the flight line thought they heard "gunshots," initiating a response from local police, the Pentagon official said.

The base in Tucson is home to the A-10 Warthog and the infamous "boneyard" where more than 4,000 retired U.S. Air Force aircraft are kept in the desert, but can be brought back into service. About 6,500 active duty military and 1,000 Reserve and Air National Guard personnel work on the base, along with about 3,000 civilians.

Borman K-8 School is located on the base. The school went on a "soft lockdown," meaning nobody could enter or leave, and windows and doors had to stay locked, according to the Tucson Unified School District.

The Sonoran Science Academy, a charter school on the base, reported that it would not answer phones during the lockdown. Officials there said no students or staff were missing.

Fox News' Jennifer Griffin, Lucas Tomlinson and The Associated Press contributed to this report.

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