FC Schalke 04 are contenders for the Bundesliga title
An anthem sung by fans of the German football club FC Schalke 04 has drawn protests from Muslims because of its reference to the Prophet Muhammad.
The Gelsenkirchen club, which plays in Germany's top league, the Bundesliga, has asked an Islam expert to consider whether the song might be insulting.
The third verse contains the words: "Muhammad was a prophet who understood nothing about football".
"But of all the lovely colours he chose [Schalke's] blue and white," it goes.
The club has received hundreds of e-mails from angry Muslims recently, since Turkish media carried reports about the song.
Police in Gelsenkirchen, in the industrial Ruhr region of western Germany, say they are taking the Muslim complaints very seriously.
The head of Germany's Central Council of Muslims, Aiman Mazyek, said his council would not call for a ban on the anthem, but would like "an explanation of its background".
The song is called "Blue and White, how I love you" and in German the lyrics about Muhammad read: Mohammed war ein Prophet, der vom Fussballspielen nichts versteht. Doch aus all der schoenen Farbenpracht hat er sich das Blau und Weisse ausgedacht.
The German news website Deutsche Welle says the song was written in 1924 and it is not clear when the Muhammad reference made its way in.