Vandals rammed a stolen bulldozer into a former Nazi concentration camp causing about £40,000 of damage.
The unknown assailant snatched the vehicle from a construction site near the Langenstein-Zwieberge camp, central Germany, and drove it one mile across a field to the gates of what is now a memorial to the more than 2,000 people who were worked to death there.
The bulldozer was used to flatten the gate as well as some 500 metres of perimeter fence, the Local reported. The vehicle was later abandoned and set on fire nearby.
Police said the reasons for the act are not clear but it didn't show the hallmarks of a politically motivated stunt by neo-Nazi groups.
The memorial was not defaced with swastikas or other extreme-right symbols and signs and information boards were spared by the vandals.
"At this stage of the investigation, we suspect a more likely culprit is someone who started the bulldozer up and drove it a few kilometres as a prank. We don't have any other leads," a police spokesman told local radio MDR, the Telegraph reported.
Langenstein-Zwieberge was an under-camp of the larger Buchenwald concentration camp build towards the end of the Second World War.
More than 7,000 prisoners were sent there by the Nazis to dig underground tunnels, to hide weaponry and other equipment from Allied air strikes.