Police are investigating a threatening letter reportedly containing a death threat sent to QPR defender Anton Ferdinand.
The Sun tabloid said the contents of the letter were so graphic that QPR officials did not show it to the defender, who is at the centre of a race row involving John Terry.
The Premier League club contacted the police after the letter was delivered by hand to their Loftus Road ground last Friday, according to the paper.
A spokesman for Scotland Yard said: "I can confirm that officers are investigating an allegation of malicious communication."
Ferdinand, 26, was the alleged victim of a racist comment made by Terry during QPR's Premier League home match with Chelsea last month.
The 30-year-old Blues and England captain denies the claims, which are being investigated by the police and the Football Association.