FBI spokeswoman Jillian Stickels told The Associated Press on Friday the 27 photos were first posted online in 2011, but disappeared from the site because of a technical glitch. They were restored to public view once the FBI was alerted they were missing. Stickels didn't know how long they weren't visible.
RELATED: 9/11 anniversary marked with moment of silence
Several media outlets reported Thursday and Friday that the photos were previously unseen.
The photos show plane debris, damage to the building and FBI teams on the site.
Click here for more stories, photos, and video about the Sept. 11th attacks.
CORRECTION: A previous version of this story reported that the photos were newly released.