Over the last few months, China has been importing lots of commodities of all kinds.
While some of this is probably caused by an uptick in domestic demand and restocking of inventories (which contracted sharply during the winter due to the credit crisis), the consensus seems to be that much of it is due to stockpiling.
Most people think that the Chinese government is somehow behind this, pulling the strings behind the scenes. While that's presumably true for oil, Andy Xie argues that other commodities are being stockpiled by China's private sector: It's not too difficult to store copper, and even for bulky iron ore, basically all you need is a large open space and some guards to deter theft. And financing is no problem right now, due to easy money extended by China's banks.