UPDATE: Officials say the lockdown on the Davis-Monthan Air Force Base has ended.
(TUSCON, Ariz.) -- The Davis-Monthan Air Force Base in Arizona was on lockdown today as officials negotiated with a man believed armed and barricaded inside a building on the base.
The man was barricaded in the "old dorm," azcentral.com reported, based upon an unnamed source. The website, affiliated with the Arizona Republic newspaper, reported that the man had taken no hostages and that SWAT teams were in position.
A U.S. official confirmed to ABC News that an individual with a weapon was holed up in a building at the base.
The FBI, employing agents from Phoenix and Tucson, is assisting with the matter, federal law enforcement officials told ABC News.
Base officials earlier today confirmed a lockdown on the base as they tried to chase down a report of a suspicious person, possibly with a gun, going into the old dorm.
"Earlier today somebody was seen carrying something that might have been a weapon, no one knows what that was, but it's our duty to investigate," Tech. Sgt. Russ Martin said.
No shots were fired and no one was hurt, Martin said.
The base enacted its Crisis Action Mode, which included a campus-wide lockdown, automated alert messages sent to people on base and the response of emergency vehicles to the base.
An individual on base told ABC News that he had received an email saying to stay inside, away from the windows, but had not been told about a shooter.
An individual seen being loaded into an ambulance during the lockdown was a woman who went into labor during the lockdown -- simply a case of "bad timing," Martin said.
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