The British campaign group Led By Donkeys has claimed responsibility for the stunt that authorities say may have breached German laws on the use of symbols linked to illegal organizations.

“Last night we were up on the Tesla Gigafactory in Berlin, the main European manufacturing site of Elon Musk’s car business,” the group wrote in an email to supporters on Thursday. “It’s the company that makes him the world’s richest man, money he is increasingly using to boost the far-right across Europe.”