Attack on Titan: Before the Fall (Manga)

A manga series entitled Attack On Titan: Before the Fall is currently ongoing. The first chapter has been released and you can read it here http://www.mangareader.net/attack-on-titan-before-the-fall It is an official manga written by Isayama Hajime.

Plot
Seventy years before the fall of Wall Maria a cover-up happened. A cover up of the breach of the walls by a titan.