Travis Air Force Base in Fairfield is responded to what it is describing as a 'real world security incident' on Wednesday.

A loud speaker was used to warn people on base of an active shooter, the base told ABC10 reporter Gabrielle Karol. The base also said no casualties have been reported.

Around 5:00 p.m. it was announced the lock down was lifted.

Earlier in the week the base announced it will be conducting emergency drills on Wednesday and Thursday. It has been confirmed with the base this incident is not a part of its planned drill.

"Travis Air Force Base is currently responding to a security incident," Fairfield Police Department said. "More details will be released as they become available. The public is being asked to stay away from the base to ensure emergency responders can respond accordingly."

No other information has been released at this time.

This is a developing story. Refresh for more details as they come in.