KHLOE KARDASHIAN Suspicious White Powder INVESTIGATED BY FBI

Sources say ... the letter arrived to the studio this morning ... and the FBI arrived to inspect the mystery substance. Law enforcement determined the powder was harmless.  This is the 3rd instance we know of where a suspicious white powder was sent to the CBS studio -- two letters were sent to Bristol Palin, and just as in this case the white substance turned out to be harmless talcum powder.