A false alarm triggered a security lockdown for about two hours at Travis Air Force Base in northern California on Wednesday in response to erroneous reports of gunfire, base officials said.
Travis Air Force Base northeast of San Francisco is no longer on lockdown.
Base officials asked for the public to stay away to ensure emergency responders can do their work.
The scare came as the base was in the midst of a multi-day exercise to test and train personnel to respond to emergencies.
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The main gate to the base was closed as a result of the investigation.
4 p.m. UPDATE: A witness at the scene says there is an active shooter situation at the shopping center on base.
Rep. John Garamendi of California said that a mistaken report of a shooting led to the heightened state of the incident, according to the Associated Press. "Await further info", a tweet from the base's official account said. One user posted a video that captures the loudspeaker at the base saying, "Real world lockdown".
The base posted on Twitter and Facebook at about 3:40 p.m. Wednesday afternoon to say everyone on base has been ordered to shelter in place and has been ordered to lock doors and windows.