A concerned resident called Bochum police at 11 pm on Sunday, worried that someone was trying to get into the house with a drill. The noise was so loud, Die Welt newspaper reported on Monday, that the tiles in his flat were vibrating.
He joined the officers in scouring the house to track down the mysterious noise, which grew ever louder the further down the building they were.
Eventually they ended up in the building's communal cellar, expecting to find a determined burglar armed with an electric drill.
But on entering there was nothing to be seen apart from a lone vibrator that had fallen off a shelf, turned itself on and rolled up against pipes.
The police officers couldn't help but crack a smile, Die Welt said.
This was not the first case of a rogue vibrator causing trouble in the North Rhine-Westphalian city – in March 2010 a woman rang the police, terrified by a noise in her bedroom.
It turned out that is was not an intruder, but an electric sex toy that she kept in a drawer.