Keys to her car and room were found in the armory where she was working earlier in the day along with her identification card and wallet, the release said.
Guillen, a private first class, was last seen wearing a black T-shirt, according to the release.
“An extensive search is underway by military members, as well as civilian and military police,” the release said.
Guillen is described as 5 feet 2 inches, 126 pounds with black hair and brown eyes.
Officials are asking anyone with information regarding Guillen’s whereabouts to call the Army CID special agents or military police.