The base said on its Twitter account that all personnel were free to resume work after the nearly two-hour lockdown.
Officials had sent an email to personnel shortly after 10 a.m. MST with the word “LOCKDOWN” written three times in all-caps, followed by an alert of an “active shooter.”
They later said in a news release that reports of gunshot sounds were unconfirmed.
Two schools are also inside the base. Both said all students were safe and unaccounted for.
About 10,500 people work on the Tucson base.
The base is home to the 355th Fighter Wing, which provides training and deploys the A-10 jet.