From the "shorts", those who have sold the contracts. It's rumored that JPMorgan is the largest seller of silver contracts. It's also rumored that they are working in conjunction with the central banks flush with newly printed cash.
http://www.youtube.com/watch?v=9FGVtJRWP6k
The Wicked Witch Explains Her Motives..... This video explains why JPM shorts silver
The “wicked witch” is Blyth Masters who heads commodities at JPM... she also was one of the inventors of credit default swaps