The Metropolitan Police have launched an investigation into allegations that referee Mark Clattenburg racially abused Chelsea midfielder John Obi Mikel.
The Football Association has also opened an investigation following suggestions that Clattenburg used "inappropriate language" towards Mikel and fellow Blues midfielder Juan Mata during their defeat to Manchester United on Sunday.
However, the police have now followed suit to determine whether a racially aggravated comment occurred during the Premier League encounter.
Clattenburg strongly denies all allegations made against him, but he has been stood down from officiating this weekend.
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