TUCSON, Ariz. - A barricade situation is over at Davis-Monthan Air Force Base, but authorities aren't immediately releasing any details.
A military official said earlier Friday that a man with a gun was holed up in a building at the sprawling base on the outskirts of Tucson and that the base was locked down for several hours.
The reports prompted a frenzy of activity at the base and in the news media amid unsubstantiated reports that someone had been shot.
Information from the base has been spotty and even contradictory at times Friday. The base first said it was in lockdown over an unspecified security situation. Officials speaking anonymously indicated that the lockdown was prompted by a witness who said they saw someone entering a base building with a weapon.
The Air Force then corroborated that version of events, but stressed that no shots had been fired, the report as a whole was unconfirmed and seemed to suggest that the ongoing security measures were being taken out of an abundance of caution.
But then a military official told the media that there was indeed a man with a gun holed up in a building on the edge of the base. The Tucson police department says its SWAT team, hostage negotiations unit and bomb squad were on stand-by to help out. The FBI also had personnel on the scene.
Now base officials won't say if there was a gunman or if there were any arrests.
The base commander was scheduled to hold a news conference Friday evening to discuss the situation.
Traffic into and out of the base was restricted and several schools on the premises were put on lockdown.
Someone claimed to have seen a man entering the first floor of one of the buildings on the base with a rifle, prompting the initial lockdown, an Air Force law enforcement source told CBS News. Security personnel are interviewing the witness.
Spokesman Senior Airman Timothy Dunaway says traffic has been reduced to a single point entry but he refused to elaborate. He says the Sonoran Science Academy as well as two elementary schools on the base are also on lockdown.
Tucson fire spokeswoman Trish Tracy says that besides the ambulances, two fire trucks were dispatched to the base. The Air Force said in a statement that one of the ambulances seen leaving the base was taking a pregnant woman to the hospital and had nothing to do with the security alert.
Davis-Monthan is adjacent to the Pima Air & Space Museum and the "boneyard" for old military and government airplanes that is a popular destination for aviation enthusiasts.
The base is the home of the 355th Fighter Wing, and provides attack airpower, combat support and medical forces, according to the base's Facebook page.
Security at military bases has gained more attention in the last two years since an Army major went on a rampage at Fort Hood in Texas in 2009. Maj. Nidal Hasan is charged with 13 counts of premeditated murder and 32 counts of attempted premeditated murder in the shooting spree. Investigators have foiled other plots against military bases in other parts of the country since Sept. 11.