An Alabama National Guard unit is under investigation, the U.S. Army said, after a social media post by the unit appeared to show one of its soldiers wearing a Nazi symbol o his battle helmet.

The post has since been deleted, but not before it was shared widely on social media by others.

The image appeared to show a Nazi SS Totenkopf symbol on the helmet of a member of the 20th Special Forces Group that is headquartered in Birmingham. The symbol includes a skull and crossbones and was used by Adolf Hitler’s elite unit, reported the Military Times.

The U.S. Army confirmed that the symbol is unauthorized and not allowed to be used.