Police are investigating after a "malicious
communication" - reportedly containing a bullet - was sent to Queens
Park Rangers' training ground.
The Met would not reveal the letter's contents or the intended recipient.
The Fulham Chronicle says the bullet was sent in a letter addressed to QPR defender Anton Ferdinand.
QPR play Chelsea in the FA Cup at Loftus Road on Saturday for the first time since
John Terry was charged with racially abusing Ferdinand.
"We are investigating an allegation of malicious communication received today at QPR FC," police said.
QPR released a statement following inquiries about the
incident, saying "full searches" would be carried out as spectators
arrived for the Chelsea match which kicks off at 1200 GMT.
"We would like to advise supporters from both QPR and Chelsea to arrive early at the stadium," the statement said.
"Full searches will be carried out ahead of your entry to the
ground, so please have your tickets to hand and be ready to be
searched. Entry to the stadium will be permitted from 10.30am for the
midday kick-off.
"We are asking for your full understanding and co-operation."
Paul Finney from the Independent Rs QPR website told BBC
Radio 5 live he was "surprised, shocked and disappointed" by the
"malicious communication" allegation.