Blac's fiance Rob Kardashian, 29, was the first to notice that the huge sum of money and several pieces of jewellery had gone missing from her Tarzana mansion in LA, reported TMZ.
A source said that there were no obvious signs of forced entry and "that has led police to believe it was someone in the couple's 'inner circle".
"Signs point to the culprit being someone close to her and Rob," the source said.
Rob and Blac currently live together at the Tarzana home.