Sept. 16, 2011— -- A lockdown was lifted at the Davis-Monthan Air Force Base in Arizona, after reports of a possibly armed intruder in a base building turned out to be unfounded.
Col. John Cherrey, commander of the 355th Fighter Squadron, came to the base's main gate at 9 p.m. ET and told local reporters that a search of the "old dorm" building did not turn up a suspect or a weapon.
"No gunman or weapon was found," Cherrey said, "and the building was declared secure."
Earlier, a U.S. official confirmed a local report that an individual with a weapon was holed up in the building.
Federal law enforcement officials told ABC News that the FBI was assisting with the matter.
The lockdown was imposed as officials 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.
Though no shots had been fired and no one was hurt, 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.
ABC News' Michael S. James contributed to this report.