A TSG 1899 Hoffenheim worker faces disciplinary procedures after admitting on Monday he had set up loudspeakers in the visitors’ stands and activated them whenever they had started to chant offensive slogans against his football club’s president Dietmar Hopp.

Media reports over the weekend included puzzled references to a shrill, deafening noise which would blast out across the Borussia Dortmund fan block whenever they started chanting anti-Hopp abuse.

Now a Hoffenheim employee has admitted setting up sirens in the visitors’ stands, and activating them whenever they started shouting. He said he did not appreciate how loud they would be, and claimed he had meant it to be a joke.

The police have now become involved after an official complaint of bodily harm from a Borussia fan who said he suffered earache after the match.

Schalke 04 fans meanwhile might have chosen a howling siren given the choice – at their team’s match against 1 FC Köln over the weekend, some were showered with faeces and urine by the opposition.

The police confirmed on Tuesday that at least one person in the Köln fan block had been seen ‘placing’ faeces into a plastic beer glass and then throwing it at his rivals. The solid organic missile was followed by at least two urine-filled plastic beer glasses.

“We as a club obviously distance ourselves from these people,” said a spokesman for 1 FC Köln fans. “This behaviour is not acceptable. There cannot be two opinions on this.”

DPA/The Local/hc