Law enforcement sources tell TMZ ... whoever stole Khloe and Lamar's jewelry knew exactly what they were looking for. The thief or thieves took only the very expensive items, leaving the rest behind. They knew exactly where to look and what to take.
What makes it look like even more of an inside job ... there was NO sign of forced entry at either home.
Our law enforcement sources believe someone from the crew of "Keeping Up with the Kardashians" is the culprit.
We're told crew members are being questioned, but so far no one has copped to the crimes.