The troops were responsible for the first in a wave of photographs which emerged in October of Germans serving in the NATO-led force in Afghanistan clowning with human skulls and bones.

The prosecutor's office in Munich said the skulls pictured in the photographs that were published in Bild newspaper were found in a lime field outside Kabul.

Skull did not come from cemetery

The area is not a cemetery, but it is strewn with skeletons -- presumably those of Russian soldiers who died during the Soviet occupation of Afghanistan in the 1980s, the Munich authorities said.

Prosecutors had investigated charges of disturbing the peace of the dead and desecrating. But in a statement, they said there was not enough evidence to link the men to "disturbing the peace of the dead." The soldiers could only be indicted if the reported offense had actually take place at a burial site, the prosecutors said.

Afghans often collect lime from the site and use it to build houses.

Obscene photographs

The photographs were taken in 2003. One of them shows a soldier mounting the skull on the front of a patrol vehicle emblazoned with both the German flag and the acronym ISAF, for the International Security Assistance Force in Afghanistan.

In another picture, a soldier in a bullet-proof vest holds a skull next to his exposed penis.

Six soldiers were suspended from the Bundeswehr as a result of the skull scandal and 23 have been under criminal investigation. Germany has 2,750 peacekeepers serving with the force and holds the command of ISAF in the north of the country.