UPDATE: Davis-Monthan Air Force Base in Arizona has lifted the lockdown and sounded the all-clear Monday afternoon. In posts on social media, the base said personnel are now "free to resume all normal operations."
In a statement, Davis-Monthan said that an airman near the base's flightline heard suspected gunshots at about 9:50 a.m. local time, and the base was locked down "out of an abundance of caution."
The base said that, in addition to checking the reported location of the suspected gunshots, security forces airmen first cleared the base's day care facilities and schools to make sure the children were safe. They then cleared the rest of the base, Davis-Monthan said.
By about 11:38 a.m. local time, security forces had finished the sweeps and the base lifted the lockdown.
Davis-Monthan is still investigating the source of the alleged gunshots.
ORIGINAL STORY: Davis-Monthan Air Force Base said on its Facebook page Mondaythat it is on lockdown following "unconfirmed reports of gun shot sounds," and advised people there to "seek shelter immediately."
Master Sgt. Neal Joiner, a spokesman for the 355th Fighter Wing at the Arizona base, said that officials are still gathering information and was unable to say anything more at this time.
Air Force Times will update this story as it learns more.
Stephen Losey is the air warfare reporter for Defense News. He previously covered leadership and personnel issues at Air Force Times, and the Pentagon, special operations and air warfare at Military.com. He has traveled to the Middle East to cover U.S. Air Force operations.